High temperature treated media

ABSTRACT

A thermally bonded filtration media that can be used in high temperature conditions in the absence of any loss of fiber through thermal effects or mechanical impact on the fiber components is disclosed. The filter media can be manufactured and used in a filter unit or structure, can be placed in a stream of removable fluid, and can remove a particulate load from the mobile stream at an increased temperature range. The combination of bi-component fiber, other filter media fiber, and other filtration additives provides an improved filtration media having unique properties in high temperature, high performance applications.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/454,171, filed Mar. 18, 2011 and claims priority to U.S.Provisional Patent Application No. 61/454,172, filed Mar. 18, 2011, thecontents of which are herein incorporated by reference in theirentirety.

FIELD OF THE INVENTION

The invention relates to a thermally formed composition in the form of aweb or layer, a filtration medium or media and a filter structure havingimproved properties. Improved permeability, high temperature strength,mechanical stability and high capacity for aerosol or particulateremoval from a moving fluid, including air, gas or liquid streams canresult from the thermally formed composition. The filter media can beformed into a variety of filter units in the form of filtration panels,cartridges, inserts, pleated forms, etc.

BACKGROUND OF THE INVENTION

Non-woven fibrous layers, webs or media have been manufactured for manyyears for many uses including filtration. An array of media that has anacceptable set of properties are available. Complexities inherent in themanufacture of these media increase costs and reduce flexibility inproduct offerings.

Such non-woven fibrous media are useful in a variety of applications,including filtration of aerosol or solid particulates from air or liquidstreams, such as dust and mist filtration, crankcase ventilation (CCV)and open crankcase ventilation (OCV). Such media can also be formed intolayered media structures.

Non-woven fibrous media can be made of natural or synthetic fibers andcan be formed into a variety of media types. One recent media type isshown in U.S. Pat. Nos. 7,314,497, 7,309,372 and 5,580,499 and generallycomprise a bi-component fiber and glass fibers that are thermally bondedinto a web. Such media have useful pore size and filtration efficienciesfrom the combined fiber component.

Many filter media grades, including bi-component fiber media, are beingused at temperatures greater than about 100° C. and are more recentlybeing used at temperatures greater than about 130° C. to 150° C. andmore. Future media will be exposed to higher temperatures and otherharsh operating conditions. At such temperatures and under suchconditions, fibrous media bonded by thermoplastic resins andthermoplastic bi-component media can soften or fail. Such softenedstructures can have reduced filtration properties, can mechanically failduring use or as a result of softening or reduced tensile strength,portions of the filtration media can be lost from the media and canenter the fluid stream causing downstream difficulties. Such problemscan occur in any application experiencing consistently elevatedoperating temperatures or experiencing periodic temperature extremes.Such media requires filtration properties sufficient to removeparticulate while maintaining low pressure drop across the media. Themedia used in CCV (Closed crankcase ventilation) or OCV (open crankcaseventilation) applications need to rapidly drain accumulated oil liquids.

One environment of interest is “under-hood” filtration that is currentlybecoming more common. Due to environmental concerns and other designcharacteristics, various types of engine filters are more commonly usedinside an engine compartment and adjacent to engine components. Inmodern engines, and in particular diesel engines, under-hoodtemperatures continue to pose operating challenges to filtrationapplications, including air filtration, oil filtration, hydraulicfiltration, crank case ventilation (OCV and CCV) applications andothers. In such engines, filtration media can operate at hightemperature. Further, after engine shutdown the filtration media areheat soaked in high temperature engine fluids (air, lubricants or fuel).Such engines must be equipped with filters and filtration media that canwithstand substantially higher heat soak temperatures.

A substantial need exists for filtration media that can withstand hightemperatures without suffering a negative performance impact infiltration properties, mechanical integrity, or without suffering lossof filtration components. A substantial need exists to reduce oreliminate glass fiber in media.

Further, making filtration media from glass fiber, however, can resultin the media shedding glass fiber from the web structure. Glass fibersleaving the filtration media can enter the downstream flow of fluid fromthe filter. The flow can direct the glass fiber into the operatingmechanism or unit associated with a filter structure. Thus, there is aneed in the industry to reduce or eliminate glass fiber in filtrationmedia.

BRIEF DESCRIPTION OF THE INVENTION

We have found a thermally bonded filter medium with improved properties.A first aspect of the medium can provide filtration properties attemperatures, for example, greater than 100° C., greater than 130° C.and often up to and greater than 150° C. in a heat soak mode or in theoperating engine or in a fluid passing through the filter medium. Thefilter structure comprises a first bi-component fiber, an optionalsecond bi-component fiber, and a staple thermoplastic fiber orcellulosic fiber that, in combination, can have improved filtrationtemperature properties and improved manufacturing character. Further,such improved high temperature media can permit the use of elements inhigher temperature conditions and can result in smaller more efficientfiltration units, permitting more flexibility in engine design andextended filter lifetime.

A second aspect of the medium is a substantially free of glass fiberthat is capable of high efficiency, mechanical stability, long life,substantial versatility and clean-ability (or regenerability) under avariety of extreme conditions, including high temperature.

We have also found a method of making the thermally bonded filtermedium, in the absence of a substantial amount of glass fiber thatresults in rapid removal of process water in the rapid and efficientformation of a wet dewatered web, rapid drying and efficient thermalbonding of the formed web into the final dried filter media. The processinvolves combining a first bi-component fiber source, an optional secondbi-component fiber source, and an effective web forming amount of astaple fiber to form an aqueous furnish, forming a wet web from theaqueous furnish on an inclined screen paper making machine, removingprocess water from the wet web, drying the wet web and thermallyprocessing the formed web into a finished media. We have found that thecombination of these fibers rapidly and efficiently forms a highlyuseful filtration medium.

The media of the invention can be used in a variety of applications forthe purpose of removing solid or liquid particulates from a variety offluid materials including gases and liquids. Further, the filter mediaof the invention can be used in a variety of filter element typesincluding flat media, pleated media, flat panel filters, cylindricalspin-on filters, z media pleated filters and other embodiments whereinthe fiber and additive components provide useful properties.

The media of the invention comprises an effective amount of abi-component fiber. The term “bi-component fiber” means a fiber havingat least one thermoplastic binder polymer portion with a melting pointand a second thermoplastic structural polymer portion with a differentand higher melting point than the binder polymer portion. The physicalconfiguration of these fibers is typically in a “side-by-side” or“sheath-core” structure. In side-by-side structure, the twothermoplastic polymer resins are typically extruded in a connected formin a side-by-side structure. The lower melting polymer acts as a binderand the higher melting polymer acts as a structural material. One couldalso use lobed fibers where the lobes, or tips, are formed from thelower melting point polymer. In the sheath-core structure, the corecontains the higher, structural fiber melting point and the sheathcontains the lower, bonding layer melting point.

The term “in the substantial absence of glass fiber” or “substantiallyfree of glass fiber” is intended to mean that the filtration medium doesnot contain a significant amount of glass fiber that contributes tofilter properties to any substantial extent. Filtration properties ofthe media are derived from the bi-component fibers, the staple fibersand other secondary fibers used in the manufacture of the filter media.Of course, insignificant amounts of glass fibers can be introduced intothe web without forming a media that relies on glass fibers for anysubstantial increment of filtration properties

An “element” is a filter portion including the web or medium of theinvention. A filter generally includes an element in a structure thatcan be made in a manufacturing operation.

As used herein, the term “fiber” or “fiber source” indicates a largenumber of compositionally related fibers such that all the fibers fallwithin a range of fiber sizes or fiber characteristics distributed abouta mean or median fiber size or characteristic. Such fibers arecharacterized by an average diameter and aspect ratio and are madeavailable as a distinct raw material. Blends of one or more of suchsources do not read on single sources.

“Glass fiber” means fiber of various diameters and lengths made usingglass of various types.

The media of the invention can include a “staple fiber”. Staple fibersare single component and non-glass fibers, other than bicomponent fiber,common in media having suitable diameter, length and aspect ratio foruse in filtration applications. Staple fibers provide pore size controland cooperate with the other fibers in the media to result in a media ofsubstantial flow rate, high capacity, substantial efficiency, and highwet strength. The careful selection of staple fiber can also improvemanufacturing of the materials of the invention. Examples of usefulstaple fibers in the filter media of the invention are cellulosic andpolyester fibers. Cellulosic fibers include cotton fibers, such ascotton linter fibers. Other useful staple fibers include syntheticpolymeric fibers such as nylon fibers, polyurethane fibers, and thelike.

As used herein, the term “secondary fibers” can include a variety ofdifferent fibers from natural, synthetic, or specialty sources. Suchfibers can be thermoplastic and are used to obtain a thermally bondedmedia sheet, media, or filter, and can also aid in obtaining appropriatepore size, permeability, efficiency, tensile strength, compressibility,and other desirable filter properties. The medium of the invention isengineered to obtain the appropriate solidity, thickness, basis weight,fiber diameter, pore size, efficiency, permeability, tensile strength,and compressibility to obtain efficient filtration properties when usedto filter a fluid stream.

As used herein, the term “solidity” means a solid fiber volume dividedby the total volume of the filter medium, usually expressed as apercentage. The solidity of media used in filtering a dust from an airstream can be different from the solidity of media used for filteringaqueous or oily aerosol from an air stream. Further, the solidity ofmedia used to remove particulates from a liquid stream can be differentthan the solidity of media used to remove particulates from a gaseousstream. Each application of the technology of the invention is directedto a certain set of operating parameters as discussed below.

As used herein, the term “web” relates to a sheet-like or planarstructure having a thickness of greater than about 0.05 mm. Thisthickness dimension can be at least 0.05 mm, at least 0.08 mm, and atleast 0.1 mm, for example. This thickness dimension may be no more than2 cm, no more than 1 cm, or no more than 5 mm for example. The lengthand width of the web is not limited and can be an indeterminate orarbitrary choice. Such a web is flexible, machineable, pleatable filtermedia that is otherwise capable of forming into a filter element orfilter structure. The web can have a gradient region and can also have aconstant region

As used herein, the plural term “filter media” or singular term “filtermedium” relate to a web having at least minimal permeability andporosity to be useful in a filter element and is not a substantiallyimpermeable layer such as conventional paper, coated stock or newsprintmade in a conventional paper making wet laid processes.

As used herein, the term “fiber morphology” means the shape, form orstructure of a fiber. Examples of particular fiber morphologies includetwist, crimp, round, ribbon-like, straight, or coiled. For example, afiber with a circular cross-section has a different morphology than afiber with a ribbon-like shape.

As used herein, the term “fiber size” is a subset of morphology andincludes “aspect ratio,” i.e., the ratio of length to diameter.“Diameter” refers either to the average diameter of a substantiallycircular cross-section of a fiber, or to a largest cross-sectionaldimension of a non-circular fiber.

As used herein, the term “fiber composition” means the chemical natureof the fiber and the fiber material or materials, including thearrangement of fiber materials. The fiber composition can be organic orinorganic. Organic fibers are typically natural or synthetic andpolymeric or bio-polymeric in nature. Examples of fiber compositionsinclude glass, cellulose, hemp, abacus, a polyolefin, a polyester, apolyamide, a halogenated polymer, a polyurethane, or a combination,blend, or alloy thereof. Inorganic fibers are made of glass, metals andother non-organic carbon source materials.

As used here, the term “surface loading”, “surface media” or “surfaceloading media” refer to media that substantially accumulates itsparticle loading on the surface and not within the media thickness ordepth.

As used herein, the term “depth media”, “depth loading layer”, or “depthloading media” refers to a filter media in which a filtered particulateis acquired and maintained throughout the thickness or z-dimension ofthe depth media. In general, a depth media arrangement can be designedto provide loading of particulate materials substantially through itsvolume or depth. Thus, such arrangements can be designed to load with ahigher amount of particulate material, relative to surface-loadedsystems, when full filter lifetime is reached. While some of theparticulate may in fact accumulate on the surface of the depth media, adepth media has the ability to accumulate and retain the particulatewithin the thickness of the depth media. In many applications,especially those involving relatively high flow rates, depth media canbe used. Depth media is generally defined in terms of its porosity,density or percent solids content. For example, a 2-3% solidity mediawould be a depth media mat of fibers arranged such that approximately2-3% of the overall volume comprises fibrous materials (solids), theremainder being air or fluid space. Another useful parameter fordefining depth media is fiber diameter. If percent solidity is heldconstant, but fiber diameter (size) is reduced, pore size is reduced;i.e. the filter becomes more efficient and will more effectively trapsmall particles. A typical conventional depth media filter is arelatively constant (or uniform) density media, i.e. a system in whichthe solidity of the depth media remains substantially constantthroughout its thickness. However, in some depth media, one or moregradients can exist. For example, the concentration of a fiber canchange from a first upstream surface to a second downstream surface;that is, through the thickness of the medium.

As used herein, the term “substantially constant” means that onlyrelatively minor fluctuations (no more than about 5%), if any, in anindicated property such as concentration or density, are foundthroughout the depth of the media. Such fluctuations, for example, mayresult from a slight compression of an outer engaged surface, by acontainer in which the filter media is positioned. Such fluctuations,for example, may also result from the small but inherent enrichment ordepletion of fiber in the web caused by variations in the manufacturingprocess. A medium can have a region that is a substantially constantregion of concentration of a fiber.

As used herein, the terms “loading media”, “loading layer”, “efficiencymedia” or “efficiency layer” refers to filter elements having acombination of at least two different media or media layers, where onemedia has a smaller average pore size and is referred to as anefficiency layer and the media having the larger average pore size isreferred to as the loading layer, loading media, or depth loading media.The loading layer is typically followed in a fluid pathway by theefficiency layer. The efficiency layer has suitable porosity,efficiency, permeability and other filtration characteristics to removeany remaining particulate from the fluid stream as the fluid exits theloading layer

For the purpose of this disclosure, the term “pore size” refers tospaces formed by fibrous materials within the media. The pore size ofthe media can be estimated by reviewing electron photographs of themedia. The average pore size of a media can also be calculated using aCapillary Flow Porometer having model no. APP 1200 AEXSC available fromPorous Materials Inc. of Ithaca, N.Y.

For the purpose of this disclosure, the term “bonded fiber” indicatesthat in the formation of the media or web of the invention, fibrousmaterials form a physical or chemical bond to adjacent fibrousmaterials. Such a bond can be formed utilizing the inherent propertiesof the fiber, such as by melt fusing the lower melting component of abi-component fiber. Alternatively, the fibrous materials of the web ormedia of the invention can be bonded using separate resinous bindersthat are provided in some cases in the form of an aqueous dispersion ofa binder resin. Alternatively, the fibers of the invention can also becross linked using crosslinking reagents, bonded using an electron beamor other energetic radiation that can cause fiber to bond, through hightemperature bonding, or through any other bonding process that can causeone fiber to bond to another.

As used herein, the term “source” is a point of origin, such as a pointof origin of a fluid flow stream comprising a fiber. One example of asource is a nozzle. Another example is a headbox.

As used herein, the term “furnish” means a relative dilute blend offibers and liquid (less than 10 wt. % solids; often less than 5 wt. %solids and often less than 1 wt. % solids). In some embodiments, theliquid includes water. In some embodiments, the furnish liquid is waterand is an “aqueous furnish”.

As used herein the term “wet layer” means a layer made from a furnish byremoving water or aqueous media from the furnish, leaving the wet fiberin the form of a “wet layer.” This wet layer is dried to form themedium.

“Machine direction” is the direction parallel to the direction that aweb travels through an apparatus, such as an apparatus that is producingthe web. In some embodiments, the machine direction is the direction ofthe longest dimension of the web.

The media of the invention can be used in a variety of applications forthe purpose of removing solid or liquid particulates from a variety offluid materials including gases or liquids. Further, the filtered mediumof the invention used in a variety of filter element types includingflat media, wraps, pleated media, flat panel filters, cylindricalspin-on filters, z media pleated filters and other embodiments whereinthe fiber and additive components provides useful properties even in theabsence of glass fiber component.

We have found that the careful selection of one or more staple fibersmade of polyester, cotton and other sources can result in asubstantially improved filter media properties or improved manufacturingprocessing and yield. The media can also comprise a fluorochemicaltreatment. We have found that these fluorochemical media havesubstantially improved durability, and can experience improved pressuredrop during operation at similar or improved efficiencies and when usedin crank case ventilations can have reduced mass increase due to oilretention and substantially improved oil drainage.

DETAILED DESCRIPTION

The media include nonwoven webs comprising a thermally bonded webcomprising a first bicomponent fiber and an optional second bicomponentfiber or staple fiber that can function at elevated temperatures. Themedia of the invention comprises a thermally bonded web comprising abi-component fiber with high temperature sheath melting properties thatcan be combined with staple media fibers or secondary fibers, and can besubstantially free of glass fiber. In one embodiment, the bi-componentfiber(s) are combined with a staple polyester fiber. In anotherembodiment, the bi-component fiber(s) are combined with a staplecellulosic fiber, preferably a cotton linter fiber. In a thirdembodiment, a method of forming the thermally bonded web comprisescombining a bi-component fiber in an aqueous furnish with other staplefibers and forming the web using conventional inclined screen papermaking machines. A final embodiment comprises a method of filtering amobile fluid.

The filter materials described herein (filter medium or media) can beused in a variety of filter applications, including but not limited topulse cleaned and non-pulse cleaned filters for dust collection, OCV andCCV applications, in gas turbines and engine air intake or inductionsystems, gas turbine intake or induction systems, heavy duty engineintake or induction systems, light vehicle engine intake or inductionsystems, vehicle cabin air, off road vehicle cabin air, disk drive air,photocopier-toner removal, and HVAC filters in both commercial orresidential filtration applications. In general, such filter elementscomprise a dense web or mat of bi-component fiber with cellulose,synthetic or other fibers oriented across a gas stream carryingparticulate material. The web or element is generally constructed to bepermeable to the gas flow, and to also have a sufficiently fine poresize and appropriate porosity to inhibit the passage of particlesgreater than a selected size there-through. As the gases (fluids) passthrough the web or element, the upstream side of the web operatesthrough diffusion and interception to capture and retain selected sizedliquid or solid particles from the gas or liquid (fluid) stream. Theparticles can be collected as a cake on the upstream side of the“surface loading” web or can be collected through the “depth loading”aspect of the filter media.

In general, the filter materials described herein can be used to filterair and gas streams that often carry particulate material entrainedtherein. In many instances, removal of some or all of the particulatematerial from the stream is necessary for continued operations, comfortor aesthetics. For example, air intake streams to the cabins ofmotorized vehicles, to engines for motorized vehicles, or to powergeneration equipment; gas streams directed to gas turbines; and, airstreams to various combustion furnaces, often include particulatematerial. In the case of cabin air filters, it is desirable to removethe particulate matter for comfort of the passengers and/or foraesthetics. With respect to air and gas intake streams to engines, gasturbines and combustion furnaces, it is desirable to remove theparticulate material because it can cause substantial damage to theequipment involved.

In other instances, production gases or off gases from industrialprocesses or engines may contain particulate material. Before such gasescan be, or should be, discharged through various locations in downstreamequipment or to the atmosphere, it may be desirable to obtain asubstantial removal of particulate material from those streams.

In general, the filter materials described herein can be applied tofilter liquid systems. In liquid filtering techniques, the collectionmechanism is believed to be sieving when particles are removed throughsize exclusion. In a single layer the efficiency is that of the layer.The composite efficiency in a liquid application is limited by theefficiency of the single layer with the highest efficiency. The liquidscould be directed through the media according to the invention, withparticulates therein trapped in a sieving mechanism. In liquid filtersystems, i.e. wherein the particulate material to be filtered is carriedin a liquid, such applications include aqueous, non-aqueous, and mixedaqueous/non-aqueous applications such as water streams, lube oil,hydraulic fluid, fuel filter systems or mist collectors, for example.Aqueous streams include natural and man-made streams such as effluents,cooling water, process water, etc. Non-aqueous streams include gasoline,diesel fuel, petroleum and synthetic lubricants, hydraulic fluid andother ester based working fluids, cutting oils, food grade oil, etc.Mixed streams include dispersions comprising water in oil and oil inwater compositions and aerosols comprising water and a non-aqueouscomponent.

Fluid (liquid and gaseous) streams carry substantial amounts ofparticulates as solids, as aerosol liquids, or both. The majority of theliquid droplets within the aerosol is generally less than 100 micronsbut can be within the size of 0.01 to 50 microns, or 0.1-5 microns. Inaddition, such streams also carry substantial amounts of fineparticulate contaminant, such as carbon contaminants. Such contaminantsgenerally can be a large as 100 microns and can have an average particlesize of about 0.5-3 microns. The filter materials described herein areadapted for the purpose of removing particulates from fluid streamshaving a particle size of about 0.01 to 100 micrometers, from gasstreams containing liquids in the form of a mist having droplet size ofabout 0.01 to 100 micrometers, from aqueous streams having a particlesize of about 0.1 to 100 micrometers from non-aqueous streams having aparticle size of about 0.05 to 100 micrometers or from fuel, lubricantor hydraulic streams having a particle size of about 0.05 to 100micrometers.

A variety of efforts have been directed to reducing the amount ofcontaminants in many filtered systems. The variables that affect removalinclude the following: (a) size/efficiency concerns; that is, a desirefor good efficiency of separation while at the same time avoidance of arequirement for a large separator system; (b) cost/efficiency; that is,a desire for good or high efficiency without the requirement ofsubstantially expensive systems; (c) versatility; that is, developmentof systems that can be adapted for a wide variety of applications anduses, without significant re-engineering; and, (d)cleanability/regeneratability; that is, development of systems which canbe readily cleaned (or regenerated) if such becomes desired, afterprolonged use.

An additional aspect of the invention comprises a preferred method offiltering with crankcase ventilation (OCV and CCV) filters. Filter mediain arrangements to filter engine gasses including crankcase gases canalso be used. The preferred media is made in sheet form from a wet laidprocess and is incorporated into filter arrangements, in a variety ofways, for example by a wrapping or coiling approach or by providing in apanel construction.ilter constructions for preferred uses to filterblow-by gases from engine crankcases are provided. Also provided arepreferred filter element or cartridge arrangements including thepreferred type of media.

We have found that by blending various proportions of bi-component andstaple or media fiber(s) that substantially improved strength andfiltration at elevated temperatures can be obtained. Further, avoidingthe use of substantial amounts of glass fiber and blending various fiberdiameters can also result in enhanced properties.

Wet laid or dry laid processes can be used. In one embodiment to makethe filter media, a fiber mat is formed using either wet or dryprocessing. The mat is heated to melt thermoplastic materials to formthe media by internally adhering the fibers. The bi-component fiber usedin the media permits the fiber to fuse into a mechanically stable sheet,media, or filter. The bi-component fiber having a thermally bondingexterior sheath (or other bi-component form) causes the bi-componentfiber to bind with other fibers in the media layer. In less preferredembodiments, the bi-component fiber can be used with an aqueous orsolvent based resin and other binders to form the medium.

In the preferred method of wet laid processing, the medium is made froma dilute (0.05 to 5 wt. % solids in the furnish) aqueous furnishcomprising a dispersion of fibrous material in an aqueous medium. Theaqueous liquid of the dispersion is generally water, but may includevarious other materials such as pH adjusting materials, surfactants,defoamers, flame retardants, viscosity modifiers, media treatments,colorants and the like. The aqueous liquid is usually drained from thedispersion by conducting the dispersion onto an inclined screen or otherperforated support retaining the dispersed solids and passing the liquidto yield a wet paper composition. The wet composition, once formed onthe support, is usually further dewatered by vacuum or other pressureforces and further dried by evaporating the remaining liquid. Afterliquid is removed, thermal bonding takes place typically by melting someportion of the thermoplastic fiber, resin or other portion of the formedmaterial. The melt material binds the component into a layer.

The media described herein can be made on equipment of any scale fromlaboratory hand-screen or hand sheet proportions to commercial-sizedpapermaking. For a commercial scale process, the bi-component mats aregenerally processed through the use of inclined screen papermaking-typemachines such as commercially available Fourdrinier, wire cylinder,Stevens Former, Roto Former, Inver Former, Venti Former, and inclinedDelta Former machines. Preferably, an inclined Delta Former machine isutilized. The general process involves making a dispersion ofbi-component fibers, staple or media fibers, or other medium material inan aqueous liquid, draining the liquid from the resulting dispersion toyield a wet composition, and adding heat to form, bond and dry the wetnon-woven composition to form the medium. After formation, the wet ordry web can be treated with additive materials to provide addedproperties.

Preferably, the filtration media of the invention is typically wet laidand is made up of randomly oriented array of a combination ofbi-component fiber(s) and staple fiber, such as a polyester orcellulosic fiber. These fibers are bonded together using the fusiblepolymer in the bi-component fiber and in some embodiments, with theaddition of a binder or resin. The preferred web is free of resinbinder.

In one embodiment, the media that can be used in the filters and methodsdescribed herein comprise a staple fiber, a bi-component binder fiber, abinder and other components. The staple fiber can include organic fiberssuch as natural and synthetic fibers including polyolefin, polyester,nylon, cotton, cotton fleece or linters, wool, etc. fibers. The mediafiber of the invention can also include a minor amount (often less than5 wt. %) of inorganic fiber such as metal, silica, boron, carbon, andother related fibers.

The filter media of the present invention is typically suited for highefficiency filtration properties such that fluids, including air andother gasses, aqueous and non-aqueous fuel, lubricant, hydraulic orother such fluids can be rapidly filtered to remove contaminatingparticulates.

Piston engines including pressure-charged diesel engines often generate“blow-by” gases, i.e., a flow of air-fuel mixture leaking past pistonsfrom the combustion chambers. Such “blow-by gases” generally comprise agas phase, for example, air or combustion off gases, carrying: (a)hydrophobic fluid (e.g., oil, including fuel aerosol) principallycomprising 0.05-10.0 micron droplets (principally, by number); and (b)carbon contaminant from combustion, typically comprising carbonparticles, a majority of which are conventionally about 0.1-1.0 micronsin size. Such “blow-by gases” are generally directed outwardly from theengine block, through a blow-by vent.

When the term “hydrophobic fluids” is used in reference to the entrainedliquid aerosol in gas flow, reference is meant to non-aqueous fluids,especially oils. Generally, such materials are immiscible in water.Herein the term “gas” or variants thereof, used in connection with thecarrier fluid, refers to air, combustion off gases, and other carriergases for the aerosol.

Engines operating in such systems as trucks, farm machinery, boats,buses, and other systems generally comprising piston (gasoline anddiesel) engines, High pressure diesel engines experience significant airor CCV or OCV gas flows contaminated as described above. For example,flow rates can be about 2-50 feet per minute (fpm) or 0.6-15 m-min⁻¹,typically 5 to 10 fpm or 1.6-3.2 m-min⁻¹. In a turbocharged dieselengine, air is taken to the engine through an air filter, cleaning theair taken in from the atmosphere. A turbo pushes clean air through afilter into engine. The air undergoes compression and combustion byinclusion within the combustion chamber and engaging with pistons andfuel. During the combustion process, the engine gives off blow-by gases.A filter arrangement is in gas flow communication with the engine andcleans the blow-by gases that are returned to the air intake, fuel orother induction system component. The gasses and air is again pulledthrough by the turbo and into the engine. The filter arrangement in gasflow communication that is used for separating a hydrophobic liquidphase from a gaseous stream (sometimes referred to herein as acoalescer/separator arrangement) is provided using the filter mediadescribed herein. In operation, a contaminated gas flow is directed intothe coalescer/separator arrangement. Within the arrangement, the fineoil phase or aerosol phase (i.e., hydrophobic phase) coalesces. Thearrangement is constructed so that as the hydrophobic phase coalescesinto droplets, it will drain as a liquid such that it can readily becollected and removed from the system. With preferred arrangements asdescribed herein below, the coalescer or coalescer/separator, especiallywith the oil phase in part loaded thereon, operates as a filter forother contaminant (such as carbon contaminant) carried in the gasstream. Indeed, in some systems, as the oil is drained from the system,it will provide some self-cleaning of the coalescer because the oil willcarry therein a portion of the trapped carbon contaminant.

The principles according to the present disclosure can be implemented insingle stage arrangements or multistage arrangements. We have found, inone embodiment, that two or more layers of filter media of thisdescription can be combined in one element. Two or more similar oridentical media can be combined in a filter structure for additiveimprovement in filtration. Alternatively, two substantially dissimilarmedia can be used to combine different types and amounts of filtration.The media can be dissimilar in any operational characteristic, includingpore size, permeability, efficiency, thickness, materials composition,etc. In one embodiment, a loading layer (with larger pore sizes than theefficiency layer) and an efficiency layer can be used, each of saidlayers having distinct structures and filtration properties, to form acomposite layer. The loading layer is followed in a fluid pathway by anefficiency layer. The efficiency layer is a highly efficient (incomparison to the loading layer) layer having suitable porosity,efficiency, permeability and other filtration characteristics to removeany remaining harmful particulate from the fluid stream as the fluidpasses through the filter structure. The loading filtration media of theinvention has a basis weight of about 30 to about 100 g-m⁻². Theefficiency layer has a basis weight of about 40 to about 150 g-m⁻². Theloading layer has an average pore size of about 5 to about 30micrometers. The efficiency layer has a pore size smaller than theloading layer that ranges from about 0.5 to about 3 micrometers. Theloading layer has a permeability that ranges from about 50 to 200ft-min⁻¹ or 15.2-61 m-min⁻¹. The efficiency layer has a permeability ofabout 5 to 30 ft-min⁻¹ or 1.52-9.14 m-min⁻¹. The loading layer or theefficiency layer of the invention has a wet bursting strength of greaterthan about 5 lb-in⁻², typically about 10 to about 25 lb-in⁻² (greaterthan 34.4 kPa or 69-172 kPa). The combined filtration layer has apermeability of about 4 to 20 ft-min⁻¹; a wet burst strength of 10 to 20lb-in⁻² (69-138 kPa) and a basis weight of 100 to 200 g-m⁻²

Briefly, the fibers can be of a variety of compositions, diameters andaspect ratios. The concepts described herein for forming a useful mediain a nonwoven web are independent of the particular fiber stock used tocreate the web. For the compositional identity of the fiber, the skilledartisan may find any number of fibers useful. Such fibers are normallyprocessed from either organic or inorganic products. The requirements ofthe specific application for the media may make a choice of fibers, orcombination of fibers, more suitable. The fibers of the media maycomprise bi-component, cellulose, hemp, abacus, a polyolefin, polyester,a polyamide, a halogenated polymer, polyurethane, acrylic or acombination thereof. Binder resins can be used to help bond the fibersinto a mechanically stable medium or web, typically in the absence ofbi-component fiber. Such binder resin materials can be used as a drypowder or solvent system, but are typically aqueous dispersions (latexor one of a number of lattices) of vinyl thermoplastic resins. Additivesof sizing, fillers, colors, retention aids, recycled fibers fromalternative sources, binders, adhesives, crosslinkers, particles, orantimicrobial agents may be added to the aqueous dispersion.

In somewhat greater detail, bi-component fibers are typically fibersmade of two polymer components. The polymer components comprise a lowermelting thermoplastic binder polymer and a higher melting structuralpolymer. Such bi-component fibers can be “core/shell” fibers or“side-by-side” fibers or “multi-lobe” fibers. The bi-component fibersoperate by providing, for example, the sheet fiber having a meltingpoint such that during the thermal forming process the fiber is heatedto a temperature such that the lower melting polymer can fuse and bondthe fibers into an intact web. Typically, the higher melting polymer isthe material that provides structural integrity to the web and does notmelt at either thermal bonding temperatures or at use temperatures. Inthe webs or media described herein, the webs comprise a bi-componentfiber and an optional second bi-component fiber. The bi-component fiberpreferably has a sheath-core structure. The preferred bi-component fiberof the invention has a higher melting characteristic i.e., the lowermelting point polymer of the bi-component fiber has a melting point ofat least 100° C., 120° C., and more preferably at least about 140° C.,and most preferably of about 140 to 160° C.; while the higher meltingpoint polymer of the bi-component fiber has a melting point of at least235° C. or about 240 to 260° C. The optional bi-component fiber has alower melting characteristic, with the lower melting point of the binderpolymer of the bi-component fiber less than that of the high temperaturefiber and can range from about 70 to 115° C. and the higher meltingpoint polymer of the bi-component fiber has a melting point greater than200° C. and of about 240 to 260° C. Further, the bi-component fibers canbe integrally mixed and evenly dispersed with the staple, pulp, orcotton fibers.

In preferred embodiments, the bi-component fibers typically have a fiberdiameter of about 5 to 50 micrometers, often about 10 to 20 micrometers,and typically in a fiber form generally have a length of 0.1 to 20millimeters or often have a length of about 0.2 to about 15 millimeters.Such fibers can be made from a variety of thermoplastic materialsincluding polyolefins (such as polyethylenes, polypropylenes);polyesters (such as polyethylene terephthalate, PET, poly-butyleneterephthalate, PBT); nylons including nylon 6, nylon 66, nylon 612, etc.Any thermoplastic that can have an appropriate melting point can be usedin the bi-component fiber while higher melting polymers can be used inthe higher melting portion of the fiber. The bicomponent fiber can have(e.g.) a PET/PET or nylon 6/nylon 6,6 structure with PET/components ofdifferent melting points or nylon. The cross-sectional structure of suchfibers can be, as discussed above, the “side-by-side” or “sheath-core”structure or other structures that provide the same thermal bondingfunction. One could also use lobed fibers where the tips have lowermelting point polymer. The he relatively low molecular weight polymer ofthe bi-component fiber can melt under sheet, media, or filter formingconditions to act to bind the bi-component fiber, and other fiberspresent in the sheet, media, or filter making material into amechanically stable sheet, media, or filter.

The bi-component (e.g., core/shell or sheath and side-by-side) fiberscan be made up similar or of different thermoplastic materials, such asfor example, polyolefin/polyester (sheath/core) bi-component fiberswhereby the polyolefin, e.g. polyethylene sheath, melts at a temperaturelower than the core, e.g. polyester or polyester/polyester ornylon/nylon materials. Typical thermoplastic polymers includepolyolefins, e.g. polyethylene, polypropylene, polybutylene, andcopolymers thereof; polytetrafluoroethylene; polyesters, e.g.polyethylene terephthalate; vinyl acetates, e.g., polyvinyl acetate,polyvinyl chloride acetate; polyvinyl butyral; acrylic resins, e.g.polyacrylate, and poly methyl acrylate, poly methyl methacrylate;polyamides, namely nylon; polyvinyl chloride, polyvinylidene chloride;polystyrene; polyvinyl alcohol; polyurethanes; cellulosic resins, namelycellulosic nitrate, cellulosic acetate, cellulosic acetate butyrate,ethyl cellulose, etc.; copolymers of any of the above materials, e.g.ethylene-vinyl acetate copolymers, ethylene-acrylic acid copolymers,styrene-butadiene block copolymers, Kraton rubbers and the like.

Particularly preferred in the fiber media described herein is abi-component fiber known as 271P available from DuPont. Others fibersinclude FIT 201, Kuraray N720 and the Nichimen 4080 and similarmaterials. These fibers demonstrate the characteristics of bonding thesheath to sheath polymer upon completion of first melt. One preferredfiber is a PET core/PET sheath fiber. Typical CCV operating temperaturesrange from about 75 to 175° C.

Media fibers are fibers that can aid in filtration or in forming astructural media layer. Such fiber is made from a number of bothhydrophilic, hydrophobic, oleophilic, and oleophobic fibers. Thesefibers cooperate with the binder, secondary fiber and the bi-componentfiber to form a mechanically stable, but strong, permeable filtrationmedia that can withstand the mechanical stress of the passage of fluidmaterials and can maintain the loading of particulate during use. Suchfibers are typically monocomponent fibers with a diameter that can rangefrom about 0.1 to about 50 micrometers and can be made from a variety ofmaterials including naturally occurring cotton, linen, wool, variouscellulosic and proteinaceous natural fibers, synthetic fibers includingrayon, acrylic, aramide, nylon, polyolefin, polyester fibers. One typeof secondary fiber is a binder fiber that cooperates with othercomponents to bind the materials into a sheet. Another type ofstructural fiber cooperates with other components to increase thetensile and burst strength of the materials in dry and wet conditions.Additionally, the binder fiber can include fibers made from suchpolymers as polyvinyl chloride, and polyvinyl alcohol. Secondary fiberscan also include inorganic fibers such as carbon/graphite fiber, metalfiber, ceramic fiber and combinations thereof. Depending on theapplication, the media or medium can comprise a wide variety of amountof secondary binder fiber. Amounts used in different media examples canbe 0.1 to 10 wt %.

Cotton is a soft, fluffy staple fiber that grows in a boll around theseeds of the cotton plant. Cotton is essentially 95% cellulose combinedwith other non-cellulosic components including natural waxes, proteinsand other biological materials. The cotton fiber of typical cultivatedcotton materials are divided into two groups. Cotton fibers can beconsidered as “fuzz” or “linter or linters”. The major distinctionbetween fuzz, cotton and linter cotton is length with pigmentation andstrength. Cotton fuzz fibers are similar to linter fibers, except theyare typically 0.33 cm compared with the 2.5 cm average length of linterfibers. Fuzz fibers tend to be about 30-40 microns in thickness, whereas linter fibers tend to be about 30 microns or less. Linter fibers arealso distinguished from fuzz fiber since linter fibers tend to beproduced close to the seed and are typically removed last in the fibermanufacture process. Both cotton “fuzz” fiber and cotton “linter” fiberare standard commercial products of cotton manufacturer and can beobtained from a variety of sources including Buckeye and SouthernCellulose. Cotton linters are fine, silky fibers which adhere to theseeds of the cotton plant after ginning. These curly fibers typicallyare less than 3 mm long. The term also may apply to the longer textilefiber staple lint as well as the shorter fuzzy fibers from some uplandspecies. Linters are traditionally used in the manufacture of paper andas a raw material in the manufacture of cellulose. Linters are oftenreferred to as “cotton wool”. This can also be a refined product(absorbent cotton in U.S. usage) which has medical, cosmetic and manyother practical uses. Preferred cotton linters have the followingcharacteristics: Length less than 5 mm or about 0.5 to 4 mm, diameterless than 80 microns or about 15 to 55 microns.

One important aspect of the media described herein that comprise cottonis the property that when combined with a bi-component fiber, the cottonlinters substantially improves manufacturing success, speed andproductivity of the wet-laid flowing processes and a staple wet layer.

Staple thermoplastic fibers include, but are not limited to, polyesterfibers, polyamide fibers, polypropylene fibers, co-polyether esterfibers, polyethylene terephthalate fibers, polybutylene terephthalatefibers, poly ether ketone ketone (PEKK) fibers, poly ether ether ketone(PEEK) fibers, liquid crystalline polymer (LCP) fibers, and mixturesthereof. Polyamide fibers include, but are not limited to, nylon 6, 66,11, 12, 612, and high temperature “nylons” (such as nylon 46) includingcellulosic fibers, polyvinyl acetate, polyvinyl alcohol fibers(including various hydrolysis of polyvinyl alcohol such as 88%hydrolyzed, 95% hydrolyzed, 98% hydrolyzed and 99.5% hydrolyzedpolymers), cotton, viscose rayon, thermoplastic such as polyester,polypropylene, polyethylene, etc., polyvinyl acetate, polylactic acid,and other common fiber types. The thermoplastic fibers are generallyfine (about 0.5-20 denier diameter), short (about 0.1-5 cm long), staplefibers, possibly containing precompounded conventional additives, suchas antioxidant, stabilizers, lubricants, tougheners, etc. In addition,the thermoplastic fibers may be surface treated with a dispersing aid.The preferred thermoplastic fibers are polyamide and polyethyleneterephthalate fibers, with the most preferred being polyethyleneterephthalate fibers.

Binder resins can be used to help bond the fiber into a mechanicallystable media layer. Such thermoplastic binder resin materials can beused as a dry powder or solvent system, but are typically aqueousdispersions (a latex or one of a number of lattices) of vinylthermoplastic resins. A resinous binder component is not necessary toobtain adequate strength for the media, but can be used. Resin used asbinder can be in the form of water soluble or dispersible polymer addeddirectly to the media web making dispersion or in the form ofthermoplastic binder fibers of the resin material intermingled with thearamid and staple or media fibers to be activated as a binder by heatapplied after the media web is formed. Resins include vinyl acetatematerials, vinyl chloride resins, polyvinyl alcohol resins, polyvinylacetate resins, polyvinyl acetyl resins, acrylic resins, methacrylicresins, polyamide resins, polyethylene vinyl acetate copolymer resins,thermosetting resins such as urea phenol, urea formaldehyde, melamine,epoxy, polyurethane, curable unsaturated polyester resins, polyaromaticresins, resorcinol resins and similar elastomer resins. The preferredmaterials for the water soluble or dispersible binder polymer are watersoluble or water dispersible thermosetting resins such as acrylicresins, methacrylic resins, polyamide resins, epoxy resins, phenolicresins, polyureas, polyurethanes, melamine formaldehyde resins,polyesters and alkyd resins, generally, and specifically, water solubleacrylic resins, methacrylic resins, polyamide resins, that are in commonuse in the papermaking industry. Such binder resins typically coat thefiber and adhere fiber to fiber in the final non-woven matrix.Sufficient resin is added to the furnish to fully coat the fiber withoutcausing film over of the pores formed in the sheet, media, or filtermaterial. The resin can be added to the furnish during papermaking orcan be applied to the media after formation.

A latex binder can be used to improve modulus or stiffness, but is notpreferred, since its use in a furnish can reduce permeability. The latexbinder, if used to bind together the three-dimensional non-woven fiberweb in each non-woven layer or used as the additional adhesive, can beselected from various latex adhesives known in the art. The skilledartisan can select the particular latex adhesive depending upon the typeof cellulosic fibers that are to be bound. The latex adhesive may beapplied by known techniques such as spraying or foaming. Generally,latex adhesives having from 15 to 25% solids are selected when a latexbinder is used. The dispersion can be made by dispersing the fibers andthen adding the binder material or dispersing the binder material andthen adding the fibers. The dispersion can, also, be made by combining adispersion of fibers with a dispersion of the binder material. Non-wovenmedia described herein can contain secondary fibers made from a numberof both hydrophilic, hydrophobic, oleophilic, and oleophobic fibers.These fibers cooperate with the staple or media fiber and thebi-component fiber to form a mechanically stable, but strong, permeablefiltration media that can withstand the mechanical stress of the passageof fluid materials and can maintain the loading of particulate duringuse. Secondary fibers are typically monocomponent fibers with a diameterthat can range from about 0.1 to about 50 micrometers and can be madefrom a variety of materials including naturally occurring cotton, linen,wool, various cellulosic and proteinaceous natural fibers, and syntheticfibers including rayon, acrylic, aramide, nylon, polyolefin, andpolyester fibers. One type of secondary fiber is a binder fiber thatcooperates with other components to bind the materials into a sheet.Another type of secondary fiber is a structural fiber that cooperateswith other components to increase the tensile and burst strength thematerials in dry and wet conditions. Additionally, the binder fiber caninclude fibers made from such polymers as polyvinyl chloride, polyvinylalcohol. Secondary fibers can also include inorganic fibers such ascarbon/graphite fiber, metal fiber, ceramic fiber and combinationsthereof.

Fluoro-organic treatments useful in this invention are small orpolymeric organic molecules having one or more C₂₋₇ fluoroaliphaticradical. The radical is a fluorinated, monovalent, aliphatic organicradical containing at least two carbon atoms. Preferably, it is asaturated perfluoroaliphatic monovalent organic radical. However,hydrogen or chlorine atoms can be present as substituents on theskeletal chain. While radicals containing a large number of carbon atomsmay function adequately, compounds containing not more than about 20carbon atoms are preferred since large radicals usually represent a lessefficient utilization of fluorine than is possible with shorter skeletalchains. The treatment composition can comprise a small molecule or apolymeric composition in combination with typical additive materials.The treatment composition can be used to prepare the furnish or to treatthe wet or dried web after formation.

The cationic groups that are usable in the fluoroorganic treatmentsemployed in this invention may include an amine or a quaternary ammoniumcationic group which can be oxygen-free (e.g., —NH₂) oroxygen-containing (e.g., amine oxides). Such amine and quaternaryammonium cationic hydrophilic groups can have formulas such as —NH₂,—(NH₃)X, —(NH(R²)₂)X, —(NH(R²)₃)X, or —N(R₂)₂→O, where x is an anioniccounterion such as halide, hydroxide, sulfate, bisulfate, orcarboxylate, R² is H or C₁₋₁₈ alkyl group, and each R² can be the sameas or different from other R² groups. Preferably, R² is H or a C₁₋₁₆alkyl group and X is halide, hydroxide, or bisulfate.

The anionic groups which are usable in the fluoroorganic treatmentsemployed in this invention include groups which by ionization can becomeradicals of anions. The anionic groups may have formulas such as —COOM,—SO₃M, —OSO₃M, —PO₃HM, —OPO₃M₂, or —OPO₃HM, where M is H, a metal ion,(NR¹ ₄)⁺, or (SR¹ ₄)⁺, where each R¹ is independently H or substitutedor unsubstituted C₁-C₆ alkyl. Preferably M is Na⁺ or K⁺. The preferredanionic groups of the fluoro-organo treatments used in this inventionhave the formula —COOM or —SO₃M. Included within the group of anionicfluoro-organic treatments are anionic polymeric materials typicallymanufactured from ethylenically unsaturated carboxylic mono- and diacidmonomers having pendent fluorocarbon groups appended thereto. Suchmaterials include surfactants obtained from 3M Corporation known asFC-430 and FC-431.

Fluororganic treatments can be used in the media. The amphoteric groupswhich are usable in the fluoro-organic treatment employed in thisinvention include groups which contain at least one cationic group asdefined above and at least one anionic group as defined above.

The nonionic groups which are usable in the fluoroorganic treatmentsemployed in this invention include groups which are hydrophilic butwhich under pH conditions of normal agronomic use are not ionized. Thenonionic groups may have formulas such as —O(CH₂CH₂)xOH where x isgreater than 1, —SO₂NH₂, —SO₂NHCH₂CH₂OH, —SO₂N(CH₂CH₂H)₂, —CONH₂,—CONHCH₂CH₂OH, or —CON(CH₂CH₂OH)₂. Examples of such materials includematerials of the following structure:F(CF₂CF₂)_(n)—CH₂CH₂O—(CH₂CH₂O)_(m)—Hwherein n is 2 to 8 and m is 0 to 20.

Other fluoroorganic treatments include those cationic fluorochemicalsdescribed, for example in U.S. Pat. Nos. 2,764,602; 2,764,603; 3,147,064and 4,069,158. Such amphoteric fluoroorganic treatments include thoseamphoteric fluorochemicals described, for example, in U.S. Pat. Nos.2,764,602; 4,042,522; 4,069,158; 4,069,244; 4,090,967; 4,161,590 and4,161,602. Such anionic fluoroorganic treatments include those anionicfluorochemicals described, for example, in U.S. Pat. Nos. 2,803,656;3,255,131; 3,450,755 and 4,090,967.

Fluoroorganic agents useful in this invention for addition to the fiberlayers are C₂₋₇ fluoroorganic molecules. Preferably, it is a chemicalwith a saturated perfluoroaliphatic organic group. However, hydrogen orchlorine atoms can be present as substituents on the skeletal chain.

Examples of such materials are duPont Zonyl FSN and duPont Zonyl FSOnonionic surfactants. Another aspect of additives that can be used inthe polymers of the invention include low molecular weight fluorocarbonacrylate materials such as 3M's Scotchgard material having the generalstructure:CF₃(CX₂)_(n)-acrylatewherein X is —F or —CF₃ and n is 1 to 7.

The preferred fluoropolymer of the invention is a polymer compositioncomprising polymer with repeating unit comprising a residue of FormulaI:

wherein S is:

-   -   wherein Q is a spacer such as —(CH₂)_(x)—, —Y—, —Y(CH₂)_(x)—,        —(CH₂)_(x)Y—, or —(CH₂)_(x)Y(CH₂)_(x)—, where Y is aryl        (preferably phenyl);    -   R is H or methyl;    -   the fluoroalkyl groups A_(f) of the present invention are        preferably C₂₋₆ fluoroalkyl, and more preferably C₄₋₆        fluoroalkyl. The fluoroalkyl groups are optionally but        preferably perfluoroalkyl (that is, all hydrogens replaced by        fluorine). The fluoroalkyl groups may contain one or two        heteroatoms selected from N and O, examples of which include but        are not limited to: -A_(f) ¹; —O-A_(f) ²; -A_(f) ¹-NA_(f) ²A_(f)        ³; -A_(f) ¹-O-A_(f) ²(-A_(f) ³)_(m)-NA_(f) ⁴A_(f) ⁵, where A_(f)        ¹, A_(f) ², A_(f) ³, A_(f) ⁴, and A_(f) ⁵ are independently each        a perfluoroalkyl; wherein A can be —(CF₂)_(x)—CF₃, where m is        defined above.

Each R₁ are independently H or halo (preferable fluoro-);

T is —O— or a covalent bond;

n is a number characteristic of acrylic polymers

m is 0 or 1 or 2;

x is 1 to 5

x+x′ is 2 to 10; and

x+x′+m is not greater than 10;

The polymers may an n characteristic of acrylic polymers and can haveany suitable molecular weight, for example, from 1,000 or 2,000 daltonsup to 5,000 daltons, or in some embodiments 1000 up to 50,000 or 100,000daltons or more.

Suitable comonomer (generally ethylenically unsaturated compounds) thatcan be used as for the comonomer containing the hydrophobic group or thecomonomer containing the attachment group includes ethylenicallyunsaturated compounds capable of copolymerizing with a (meth)acrylicacid. Examples include ethylene, vinyl acetate, vinyl chloride,vinylidene halide, (meth)acrylic acid, (meth)acrylonitrile, styrene,alphamethylstyrene, p-methylstyrene, (meth)acrylamide, N-methylol(meth)acrylamide, hydroxymethyl (meth)acrylate, hydroxyethyl(meth)acrylate, hydroxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl(meth)acrylate, polyethylene glycol (meth)acrylate, polypropylene glycol(meth)acrylate, methoxypolyethylene glycol (meth)acrylate,methoxypolypropylene glycol (meth)acrylate, N,N-dimethylaminoethyl(meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, glycidyl(meth)acrylate, tetrahydrofurfuryl (meth)acrylate, benzyl(meth)acrylate, phenoxyethyl (meth)acrylate, dicyclopentenyl(meth)acrylate, hydroxypropyltrimethylammonium chloride methacrylate,ethyltrimethylammonium chloride methacrylate, vinyl alkyl ether, alkylvinyl ether halide, butadiene, isoprene, chloroprene, maleic anhydride.(meth)acrylates, (with not fluorogroups, represented by the generalformula (Formula 4):CH₂═CA¹CO₂-alkyl  (Formula 4)[wherein A¹ represents a hydrogen atom or a methyl group, and alkylrepresents an alkyl group represented by C_(m)H_(2m)+1 (m represents aninteger of 1 to 30)]; Fluorosulfonate compounds (sulfonicacid-containing monomers)

One embodiment of the invention combines a fluorochemical compound witha urethane compound. These materials of the invention may be formed byreacting (a) a di-, tri- or higher order isocyanate with a reactivefluorochemical monofunctional compound, and (b) optionally with alimited amount of a aliphatic monofunctional compound. The reaction maybe carried out in accordance with well-known techniques such as, forexample, by condensation in a suitable solvent such as methyl isobutylketone (MIBK) using a small amount of a dibutyltin dilaurate catalyst.The urethane compound, formed in such a manner, may be emulsified inwater or dissolved in an organic solvent and may optionally be combinedwith one or more suitable surfactants may be used to stabilize theemulsion.

Preferred aliphatic isocyanates having at least three isocyanatefunctionalities may be used in the preparation of the fluorochemicalpolymer. Representative examples of suitable polyfunctional isocyanatecompounds include isocyanate functional derivatives of thepolyfunctional isocyanate compounds as defined herein. Examples ofderivatives include, but are not limited to, those selected from thegroup consisting of ureas, biurets, allophanates, dimers and trimers(such as uretdiones and isocyanurates) of isocyanate compounds, andmixtures thereof. Any suitable organic polyisocyanate, such as analiphatic, alicyclic, araliphatic, or aromatic polyisocyanate, may beused either singly or in mixtures of two or more. The aliphaticpolyfunctional isocyanate compounds generally provide better lightstability than the aromatic compounds.

Examples of useful cycloaliphatic polyfunctional isocyanate compoundsinclude, but are not limited to, those selected from the groupconsisting of dicyclohexylmethane diisocyanate (H₁₂MDI, commerciallyavailable as Desmodur™W, available from Bayer Corporation, Pittsburgh,Pa.), 4,4′-isopropyl-bis(cyclohexylisocyanate), isophorone diisocyanate(IPDI), cyclobutane-1,3-diisocyanate, cyclohexane 1,3-diisocyanate,cyclohexane 1,4-diisocyanate (CHDI), 1,4-cyclohexanebis(methyleneisocyanate) (BDI), 1,3-bis(isocyanatomethyl)cyclohexane (H₆XDI),3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, and mixturesthereof.

Examples of useful aliphatic polyfunctional isocyanate compoundsinclude, but are not limited to, those selected from the groupconsisting of 1,4-tetramethylene diisocyanate, hexamethylene1,4-diisocyanate, hexamethylene 1,6-diisocyanate (HDI), 1,12-dodecanediisocyanate, 2,2,4-trimethyl-hexamethylene diisocyanate (TMDI),2,4,4-trimethyl-hexamethylene diisocyanate (TMDI),2-methyl-1,5-pentamethylene diisocyanate, dimer diisocyanate, the ureaof hexamethylene diisocyanate, the biuret of hexamethylene1,6-diisocyanate (HDI) (available as Desmodur™ N-100 and N-3200 fromBayer Corporation, Pittsburgh, Pa.), the isocyanurate of HDI (availableas Demodur™ N-3300 and Desmodur™ N-3600 from Bayer Corporation,Pittsburgh, Pa.), a blend of the isocyanurate of HDI and the uretdioneof HDI (available as Desmodur™ N-3400 available from Bayer Corporation,Pittsburgh, Pa.), and mixtures thereof.

Suitable commercially available polyfunctional isocyanates areexemplified by Desmodur™ N-3200, Desmodur™ N-3300, Desmodur™ N-3400,Desmodur™ N-3600, Desmodur™ H (HDI), and Desmodur™ N-100, each availablefrom Bayer Corporation, Pittsburgh, Pa.

Other useful triisocyanates are those obtained by reacting three molesof a diisocyanate with one mole of a triol. For example, toluenediisocyanate, 3-isocyanatomethyl-3,4,4-trimethylcyclohexyl isocyanate,or m-tetramethylxylene diisocyanate can be reacted with1,1,1-tris(hydroxymethyl)propane to form triisocyanates. The productfrom the reaction with m-tetramethylxylene diisocyanate is commerciallyavailable as CYTHANE 3160 (American Cyanamid, Stamford, Conn.).

Because of their widespread commercial availability,polyisocyanate-functional biurets and isocyanurates derived from thehomopolymerization of hexamethylene diisocyanate are preferred for usein accordance with this invention. Such compounds are sold, for example,under the Desmodur tradename, whose products are available from MilesCorp.

Isocyanate group that remain after reaction with the fluorochemicalmonofunctional compound(s) and the aliphatic monofunctional compound(s)may optionally be blocked isocyanate groups. By the term “blockedisocyanate” is meant a (poly)isocyanate of which the isocyanate groupshave been reacted with a blocking agent. Isocyanate blocking agents arecompounds that upon reaction with an isocyanate group yield a group thatis unreactive at room temperature with compounds that at roomtemperature normally react with an isocyanate but which group atelevated temperature reacts with isocyanate reactive compounds.Generally, at elevated temperature the blocking group will be releasedfrom the blocked (poly)isocyanate compound thereby generating theisocyanate group again which can then react with an isocyanate reactivegroup. Blocking agents and their mechanisms have been described indetail in “Blocked isocyanates III.: Part. A, Mechanisms and chemistry”by Douglas Wicks and Zeno W. Wicks Jr., Progress in Organic Coatings, 36(1999), pp. 14 172.

The blocked isocyanate is generally a blocked di- or triisocyanate or amixture thereof and can be obtained by reacting an isocyanate with ablocking agent that has at least one functional group capable ofreacting with an isocyanate group. Preferred blocked isocyanates areblocked polyisocyanates that at a temperature of less than 150° C. arecapable of reacting with an isocyanate reactive group, preferablythrough deblocking of the blocking agent at a known elevated temperaturefor the blocked material. Preferred blocking agents include arylalcoholssuch as phenols, lactams such as ε-caprolactam, δ-valerolactam,γ-butyrolactam, oximes such as formaldoxime, acetaldoxime, methyl ethylketone oxime, cyclohexanone oxime, acetophenone oxime, benzophenoneoxime, 2-butanone oxime or diethyl glyoxime. Further suitable blockingagents include bisulfite and triazoles.

Sheet media described herein are typically made using papermakingprocesses. Such wet laid processes are particularly useful and many ofthe fiber components are designed for aqueous dispersion processing.However, the media can be made by air laid processes that use similarcomponents adapted for air laid processing.

The machines used in wet laid sheet making include hand laid sheetequipment, Fourdrinier papermaking machines, cylindrical papermakingmachines, inclined papermaking machines, combination papermakingmachines and other machines that can take a properly mixed paper, form alayer or layers of the furnish components, remove the fluid aqueouscomponents to form a wet sheet. A fiber slurry containing the materialsare typically mixed to form a dilute (0.05 to 5 wt. %) relativelyuniform fiber slurry. The fiber slurry is then subjected to a wet laidpapermaking process. Once the slurry is formed into a wet laid sheet,the wet laid sheet can then be dried, cured or otherwise processed toform a dry permeable, but real sheet, media, or filter. Oncesufficiently dried and processed to filtration media, the sheets aretypically about 0.25 to 2 millimeter in thickness, having a basis weightof about 20 to 200 or 30 to 150 g-m⁻². For a commercial scale process,the bi-component mats are generally processed through the use ofinclined wire papermaking-type machines such as commercially availableFourdrinier, wire cylinder, Stevens Former, Roto Former, Inver Former,Venti Former, and inclined Delta Former machines. Preferably, aninclined Delta Former machine is utilized.

A bi-component furnish used to make the layer or web can be prepared byforming pulp and staple or media fiber slurries and combining theslurries in mixing tanks, for example. The amount of water used in theprocess may vary depending upon the size of the equipment used. Thefurnish, however, is typically quite dilute and can be greater thanabout 90, 95 or 99.5 to 99.9 wt. % water. The furnish may be passed intoa conventional head box where it is dewatered and deposited onto amoving wire screen where it is dewatered by suction or vacuum to form anon-woven bi-component web. The web can then be coated with a binder byconventional means, e.g., by a flood and extract method and passedthrough a drying section which dries the mat and cures the binder, andthermally bonds the sheet, media, or filter. The resulting mat may becollected in a large roll.

The medium or media can be formed into substantially planar sheets orformed into a variety of geometric shapes using forms to hold the wetcomposition during thermal bonding. The media fiber of the invention caninclude metal, polymer and other related fibers. In forming shapedmedia, each layer or filter is formed by dispersing fibers in an aqueoussystem, and forming the filter on a mandrel with the aid of a vacuum.The formed structure is then dried and bonded in an oven. By using aslurry to form the filter, this process provides the flexibility to formseveral structures; such as, tubular, conical, and oval cylinders.

Certain preferred arrangements include filter media as generallydefined, in an overall filter construction. Some preferred arrangementsfor such use comprise the media arranged in a cylindrical, pleatedconfiguration with the pleats extending generally longitudinally, i.e.in the same direction as a longitudinal axis of the cylindrical pattern.For such arrangements, the media may be imbedded in end caps, as withconventional filters. Such arrangements may include upstream liners anddownstream liners if desired, for typical conventional purposes.

Permeability relates to the quantity of air (ft³-min⁻¹-ft⁻²) ft-min⁻¹that will flow through a filter medium at a pressure drop of 0.5 inchesof water. In general, permeability, as the term is used is assessed bythe Frazier Permeability Test according to ASTM D737 using a FrazierPermeability Tester available from Frazier Precision Instrument Co.Inc., Gaithersburg, Md. or a TexTest 3300 or TexTest 3310 available fromavailable from Advanced Testing Instruments Corp (ATI), 243 East BlackStock Rd. Suite 2, Spartanburg, S.C. 29301, (864)989-0566,www.aticorporation.com. Pore size referred to in this disclosure meansmean flow pore diameter determined using a capillary flow porometerinstrument like Model APP 1200 AEXSC sold by Porus Materials, Inc.,Cornell University Research Park, Bldg. 4.83 Brown Road, Ithaca, N.Y.

Preferred crankcase ventilation filters typically have the wet laidmedia sheet in at least a media stage stacked, wrapped or coiled,usually in multiple layers, for example in a tubular form, in aserviceable cartridge. In use, the serviceable cartridge would bepositioned with the media stage oriented for convenient drainagevertically. For example, if the media is in a tubular form, the mediawould typically be oriented with a central longitudinal axis extendinggenerally vertically.

As indicated, multiple layers, from multiple wrappings or coiling, canbe used. A gradient can be provided in a media stage, by first applyingone or more layers of wet laid media of first type and then applying oneor more layers of a media (typically a wet laid media) of a second,optionally different, type. Typically when a gradient is provided, thegradient involves use of two media types which are selected fordifferences in efficiency. This is discussed further below.

In the example arrangement described above, an optional first stage anda second stage are described. Wet laid media according to the presentdescription can be utilized in either stage. However typically the mediawould be utilized in a stage which forms tubular media stages. In someinstances when materials according to the present disclosure are used,the first stage of media, characterized as the optional first stagehereinabove, can be avoided entirely, to advantage.

The media composition of the wet laid sheets used to form a stage in afilter is provided in a form having a calculated pore size of at least10 micron, usually at least 12 micron. The pore size is typically nogreater than 60 micron, for example within the range of 12-50 micron,typically 15-45 micron. The media is formulated to have a DOP %efficiency (at 10.5 fpm for 0.3 micron particles), within the range of3-18%, typically 5-15%.

The media can comprise at least 30% by weight, typically at least 40% byweight, often at least 45% by weight and usually within the range of45-70% by weight, based on total weight of filter material within thesheet, bi-component fiber material in accord with the generaldescription provided herein. The media comprises 30 to 70% (typically30-55%), by weight, based on total weight of fiber material within thesheet, of staple or secondary fiber material having average largestcross-sectional dimensions (average diameters is round) of at least 1micron, for example within the range of 1 to 20 micron. In someinstances diameter will be 8-15 micron. The average lengths aretypically 1 to 20 mm, often 1-10 mm, as defined. This secondary fibermaterial can be a mix of fibers. Typically polyester and/or staple ormedia fibers are used, although alternatives are possible.

Typically and preferably the fiber sheet (and resulting media stage)includes no added binder other than the binder material contained withinthe bi-component fibers. If an added resin or binder is present,preferably it is present at no more than about 7% by weight of the totalfiber weight, and more preferably no more than 3% by weight of the totalfiber weight.

Typically, and preferably, the wet laid media is made to a basis weightof at least 20 lbs. per 3,000 square feet (33 gm-m⁻²; 9 kg/278.7 sq.m.), and typically not more than 120 lbs. per 3,000 square feet (195gm-m⁻²; 54.5 kg/278.7 sq. m.). Usually it will be selected within therange of 30-100 lbs. per 3,000 sq. ft. (49-163 gm-m⁻²; 14 kg-45.4kg/278.7 sq. m). Typically, and preferably, the wet laid media is madeto a Frazier permeability (feet per minute) of 40-500 feet per minute(12-153 meters/min.), typically 100 feet per minute (30 meters/min.).For the basis weights on the order of about 40 lbs/3,000 square feet-100lbs./3,000 square feet (18-45.4 kg/278.7 sq. meters), typicalpermeabilities would be about 300-600 feet per minute (92-184meters/min.). The thickness of the wet laid media sheet(s) used to laterform the described media stage in the filter at 0.125 psi (8.6millibars) will typically be at least 0.01 inches (0.25 mm) often on theorder of about 0.018 inch to 0.06 inch (0.45-1.53 mm); typically0.018-0.03 inch (0.45-0.76 mm).

Media in accord with the general definitions provided herein, includinga mix of bi-component fiber(s) and staple or media fiber(s), can be usedas any media stage in a filter as generally described above. Typically,and preferably, it will be utilized to form the tubular stage. When usedin this manner, it will typically be wrapped around a center core of thefilter structure, in multiple layers, for example often at least 5-20layers, and typically 20-70 layers, although alternatives are possible.Typically, the total depth of the wrapping will be about 0.25-2 inches(6-51 mm), usually 0.5-1.5 (12.7-38.1 mm) inches depending on theoverall efficiency desired. Typically, enough media sheets would be usedin the final media stage to provide the media stage with overallefficiency measured in this way of at least 70%, at least 85%, andtypically 90% or greater. In some instances it would be preferred tohave the efficiency at 95% or more. In the context the term “final mediastage” refers to a stage resulting from wraps or coils of the sheet(s)of wet laid media.

In crankcase ventilation filters, a calculated pore size within therange of 12 to 80 micron is generally useful. Typically, the pore sizeis within the range of 15 to 45 micron. Often the portion of the mediawhich first receives gas flow with entrained liquid for designscharacterized in the drawings, the portion adjacent the inner surface oftubular media construction, through a depth of at least 0.25 inch (6.4mm), has an average pore size of at least 20 microns. This is because inthis region, a larger first percentage of the coalescing/drainage willoccur. In outer layers, in which less coalescing drainage occur, asmaller pore size for more efficient filtering of solid particles, maybe desirable in some instances. The term X-Y pore size and variantsthereof when used herein, is meant to refer to the theoretical distancebetween fibers in a filtration media. X-Y refers to the surfacedirection versus the Z direction which is the media thickness. Thecalculation assumes that all the fibers in the media are lined parallelto the surface of the media, equally spaced, and ordered as a squarewhen viewed in cross-section perpendicular to the length of the fibers.The X-Y pore size is a distance between the fiber surface on theopposite corners of the square. If the media is composed of fibers ofvarious diameters, the d² mean of the fiber is used as the diameter. Thed² mean is the square root of the average of the diameters squared. Ithas been found that it is useful to have calculated pore sizes on thehigher end of the preferred range, typically 30 to 50 micron, when themedia stage at issue has a total vertical height, in the crankcaseventilation filter of less than 7 inches (178 mm); and, pore sizes onthe smaller end, about 15 to 30 micron, are sometimes useful when thefilter cartridge has a height on the larger end, typically 7-12 inches(178-305 mm). Taller filter stages may provide for a higher liquid head,during coalescing, which can force coalesced liquid flow, under gravity,downwardly through smaller pores, during drainage. The smallerporesallow for higher efficiency and fewer layers. In a typicaloperation in which the same media stage is being constructed for use ina variety of filter sizes, typically for at least a portion of the wetlaid media used for the coalescing/drainage in initial separation, anaverage pore size of about 30-50 microns will be useful.

Solidity is the volume fraction of media occupied by the fibersexpressed as a percentage of volume (%). It is the ratio of the fibersvolume per unit mass divided by the media's volume per unit mass.Typical wet laid materials preferred for use in media stages accordingto the present disclosure, especially as the tubular media stage inarrangements such as those described above in connection, have a percentsolidity at 0.125 psi (8.6 millibars) of under 10%, and typically under8%, for example 6-7%. The thickness of media utilized to make mediapacks according to the present disclosure, is typically measured using adial comparator such as an Ames #3W (BCA Melrose MA) equipped with around pressure foot, one square inch. A total of 2 ounces (56.7 g) ofweight is applied across the pressure foot. Typical, wet laid mediasheets useable to be wrapped or stacked to form media arrangements,according to the present disclosure, have a thickness of at least 0.01inches (0.25 mm) at 0.125 psi (8.6 millibars), up to about 0.06 inches(1.53 mm), again at 0.125 psi (8.6 millibars). Usually, the thicknesswill be 0.018-0.03 inch (0.44-0.76 mm) under similar conditions.

The media described herein have a preferred DOP efficiency at 10.5ft/minute (3.2 m-min⁻¹) for 0.3 micron particles for layers or sheets ofwet laid media. This requirement indicates that a number of layers ofthe wet laid media will typically be required, in order to generate anoverall desirable efficiency for the media stage of typically at least70%, at least 85% or often 90% or greater, in some instances 95% orgreater. In general, DOP efficiency is a fractional efficiency of a 0.3micron DOP particle (dioctyl phthalate) challenging the media at 10.5fpm. A TSI model 3160 Bench (TSI Incorporated, St. Paul, Minn.) can beused to evaluate this property. Model dispersed particles of DOP aresized and neutralized prior to challenging the media. The wet laidfiltration media accomplishes strength through utilization of addedbinders. However, this may compromise the efficiency and permeability,and increase solidity. Thus, as indicated above, the wet laid mediasheets and stages according to preferred embodiments herein typicallyinclude no added binders, or if binder is present it is at a level of nogreater than 7% of total fiber weight, typically no greater than 3% oftotal fiber weight.

Strength properties that generally define media gradings includestiffness, tensile and resistance to compression. In general,utilization of bi-component fibers and avoidance of polymeric bindersleads to a lower stiffness with a given or similar resistance tocompression and also to good tensile. Machine direction tensile is thebreaking strength of a thin strip of media evaluated in the machinedirection (MD). Reference is to Tappi 494 using the following testconditions: sample width, 1 inch (25.4 mm); sample length, 4 inch gap(101.6 mm); pull rate-2 inches/minute (50.8 mm/minute).

Modification of the surface characteristics of the fibers in media, suchas increasing the contact angle with water, should enhance the drainagecapability of the filtration media and thus the performance of a filter(reduced pressure drop and improved mass efficiency). Fluoro-organicwetting agents useful in this invention for addition to the fiber layersare C₂₋₁₂ fluoroorganic molecules. Preferably, a chemical with achemically stable saturated perfluoroaliphatic organic group is used.However, hydrogen or chlorine atoms can be present as substituents onthe skeletal chain. Various fibers are used in the design of for examplefiltration media used for low pressure filters such as mist filters orothers (less than 1 psi terminal pressure drop).

One method of modifying the surface of the fibers is to apply a surfacetreatment such as a fluorochemical or silicone containing material,0.001 to 5% or about 0.01 to 2.5% by weight of the media. The surfacecharacteristics of the fibers can be modified in a wet laid layer thatcan include bi-component fibers, other secondary fiber such as asynthetic, ceramic or metal fibers with and without additional resinbinder. The resulting media could be incorporated into filter elementstructures with a thickness generally greater than 0.05 inches oftenabout 0.1 to 0.25 inches. The media would have larger XY pore size thanconventional air media, generally greater than 10 often about 15 to 100micron, and would be composed of larger size fibers, generally greaterthan 6 micron although in certain cases small fibers could be used toenhance efficiency. The use of surface modifiers may allow theconstruction of media with smaller XY pore sizes than untreated media,thereby increasing efficiency with the use of small fibers, reduce thethickness of the media for more compact elements, and reduce theequilibrium pressure drop of the element.

In the case of mist filtration, the system can be designed to drain thecollected liquids. The opposite of drainage is mass increase or weightgain during filtration. Both maximum drainage and minimum weight gain isa desirable result of using the media and filter arrangements describedherein. Media in both the pre-filter and primary element are positionedso that the liquid can drain from the media. Important performanceproperties for these two elements are: initial and equilibriumfractional efficiency, pressure drop, and drainage ability. Importantphysical properties of the media are thickness, solidity, and strength.

The elements are typically aligned vertically which enhances thefilter's capability to drain. In this orientation, any given mediacomposition will exhibit a equilibrium liquid height which will be afunction of the XY pore size, fiber orientation, and the interaction ofthe liquid with the fibers' surface, measured as contact angle. Thecollection of liquid in the media will increase the height to a pointbalanced with the drainage rate of liquid from the media. Any portion ofthe media that is plugged with draining liquid would not be availablefor filtration thus increasing pressure drop and decreasing efficiencyacross the filter. Thus, it is advantageous to minimize the portion ofthe element that retains liquid.

The three media factors effecting drainage rate, XY pore size, fiberorientation, and interaction of the liquid being drained with thefiber's surface, can all be modified to minimize the portion of themedia that is plugged with liquid. The XY pore size of the element canbe increased to enhance the drainage capability of the media but shouldbe balanced against the resultant effect of reducing the number offibers available for filtration, and thus the potential efficiency ofthe filter. To achieve target efficiency, a relatively thick elementstructure may be needed, typically greater than 0.125 inches, due to theneed for a relatively large XY pore size. The fibers can be orientedwith the vertical direction of the media. The interaction of the liquidbeing drained with the surface of the fibers can be modified to enhancethe drainage rate.

In one application, crank case filtration applications, small oilparticle mists are captured, collect in the element and eventually drainfrom the element back into the engine's oil sump. Filtration systemsinstalled on the crank case breather of diesel engines can be composedof multiple elements, a pre-filter that removes large particlesgenerally greater than 5 microns and a primary filter that removes thebulk of the residual contamination. The primary element can be composedof single or multiple layers of media. The composition of each layer canbe varied to optimize efficiency, pressure drop and drainageperformance.

Due to filtration system size constraints, the pre and primary elementsmust be designed for equilibrium fractional efficiency or average massincrease. Equilibrium fractional efficiency is defined as the element'sefficiency once the element is draining liquid at a rate equal to thecollection rate. The three performance properties, initial andequilibrium fractional efficiency, pressure drop, and drainage ability,are balanced against the element's design to achieve optimumperformance. Thus, as an example, short elements in a high liquidloading environment must be designed to drain at a relatively fast rate.

In one preferred embodiment of the invention, the filtration medium ormedia is comprised of a thermally bonded sheet. The sheet is comprisedof about 20 to 80 wt % of a first sheath-core bi-component binder fiberand about 5 to 20 wt % of an optional second bi-component fiber. Thefirst bi-component fiber has a core polymer with a melting point ofabout 240 to 260° C. and a sheath melting point of about 140 to 160° C.The optional second bi-component fiber has a core polymer with a meltingpoint of 240 to 260° C. and a sheath polymer with a melting point atleast 10° C. less than the first bicomponent fiber and can range fromabout 70 to 140° C., 75 to 120° C., or 75 to 110° C. The media or webalso comprises about 20 to 80 wt % of a staple or media fiber. Each ofthe bi-component binder fibers has a diameter of about 5 to 50micrometers and a length of about 0.1 to 15 cm. The staple or mediafiber has a diameter of about 0.1 to 30 micrometers and an aspect ratioof about 10 to 10,000. The media has a thickness of about 0.2 to 50 mm,a solidity of about 2 to 25%, a basis weight of about 10 to 1000 g-m⁻²,a pore size of about 0.5 to 100 micrometers and a permeability of about5 to 500 ft-min⁻¹. The media is comprised of about 0.5 to 15 wt % of asecondary fiber. The media is comprised of a single layer or two or morelayers. The media is comprised of about 0.01 to 10 wt % of afluoro-organic agent. Example embodiments of different mediacompositions are shown in Table 1 and Table 2:

TABLE 1 Example of Wt. Wt. Wt. Wt. Component Useful Fiber % % % % BICO271 P  0-40  0-35  2-30  5-25 BICO TJ04 BN 20-80 25-75 20-65 25-60Staple fiber Cotton or PET 20-80 20-80 25-75 30-70 OptionalFluoro-acrylate 0.0 0.05-10  0.10-8   0.2-5  Fluorochemical

TABLE 2 Example of Component Useful Fiber Wt. % Wt. % Wt. % Wt. % BICO271 P  0-40  0-35  2-30  5-25 BICO TJ04 BN 20-80 25-75 20-65 25-60Staple Fiber Cellulose Fiber 10-40 10-40 12-38 15-35 or Cotton LinterFiber Staple Fiber PET 10-40 10-40 12-38 15-35 Monofilament

A method of the invention embodies filtering a liquid stream, where themethod is comprised of placing a filter unit into the steam andretaining solid particulate entrained in the stream on the filtersurface using filter media within the filter unit. The filter media iscomprised of a thermally bonded sheet. The thermally bonded sheet iscomprised of about 10 to 90 wt % of the total of a first and an optionalsecond bi-component binder fiber and about 10 to 90 wt % of a mediafiber. The optional fiber is used at about 0-40 wt. %, 2 to 30 wt. % or5-25 wt. %. The bi-component binder fiber has a diameter of about 5 to50 micrometers and a length of about 0.1 to 15 cm. The media fiber has adiameter of about 0.1 to 5 micrometers and an aspect ratio of about 10to 10,000. The media has a thickness of about 0.1 to 2 mm, a solidity ofabout 2 to 25%, a basis weight of about 2 to 200 g-m⁻² a pore size ofabout 0.2 to 50 micrometers and a permeability of about 2 to 200ft-min⁻¹ (0.6-60 m-min⁻¹). The liquid to be filtered may be either anaqueous liquid or a non-aqueous liquid. The media is comprised of asingle layer or two or more layers. The media is comprised of about 0.01to 10 wt % of a fluoro-organic agent.

Another method of the invention embodies filtering a gaseous fluid. Themethod is comprised of passing a gaseous mobile fluid phase containing aliquid aerosol contaminant (that can also contain a solid particulate)through a filter medium, the medium having a thickness of about 0.2 to50 mm, the medium comprising a thermally bonded sheet, and removing thecontaminant. The sheet is comprised of about 10 to 80 wt % of a firstand an optional second bi-component binder fiber and about 20 to 80 wt %of a staple or media fiber. The optional fiber at about 0-40 wt. %, 2 to30 wt. % or 5-25 wt. %. The bi-component binder fiber has a diameter ofabout 5 to 50 micrometers and a length of about 0.1 to 15 cm. The stapleor media fiber has a diameter of about 0.1 to 30 micrometers. The mediahas a solidity of about 2 to 25%, a basis weight of about 10 to 1000g-m⁻², a pore size of about 0.5 to 100 micrometers and a permeability ofabout 5 to 500 ft-min⁻¹ (1.5-152 m-min⁻¹), the mobile fluid phase havinga temperature greater than the melting point of the second component. Inone embodiment of the method described the fluid is a gas or liquid. Inone embodiment of the method described the liquid is an aqueous liquid,fuel, lubricant oil or hydraulic fluid. In one embodiment of the methoddescribed, the contaminant is a liquid or solid.

Another method of the invention embodies filtering a heated gas orliquid fluid. The method is comprised of passing a mobile fluid phasecontaining a contaminant through a filter medium, the medium having athickness of about 0.2 to 50 mm, the medium comprising a thermallybonded sheet, and removing the contaminant. The sheet is comprised ofabout 20 to 80 wt % of a biocomponent binder fiber and about 20 to 80 wt% of a staple or media fiber. The bi-component binder fiber has a firstcomponent with a melting point and a second component with a lowermelting point. The bi-component binder fiber has a diameter of about 5to 50 micrometers and a length of about 0.1 to 15 cm. The staple ormedia fiber has a diameter of about 0.1 to 30 micrometers. The media hasa solidity of about 2 to 25%, a basis weight of about 10 to 1000 g-m⁻²,a pore size of about 0.5 to 100 micrometers and a permeability of about5 to 500 ft-min⁻¹ (1.5-152 m-min⁻¹), the mobile fluid phase having atemperature greater than the melting point of the second component. Inone embodiment of the method described the fluid is a gas or liquid. Inone embodiment of the method described the liquid is an aqueous liquid,fuel, lubricant oil or hydraulic fluid. In one embodiment of the methoddescribed, the contaminant is a liquid or solid.

The medium described herein can be assembled with other conventionalfilter structures to make a filter composite layer or filter unit. Themedium can be assembled with a base layer which can be a membrane, acellulosic medium, a synthetic medium, a scrim or an expanded metalsupport. The medium can be used in conjunction with many other types ofmedia, such as conventional media, to improve filter performance orlifetime.

A perforate structure can be used to support the media under theinfluence of fluid under pressure passing through the media. The filterstructure of the invention can also be combined with additional layersof a perforate structure, a scrim, such as a high-permeability,mechanically-stable scrim, and additional filtration layers such as aseparate loading layer. In one embodiment, such a multi-region mediacombination is housed in a filter cartridge commonly used in thefiltration of non-aqueous liquids.

In one embodiment, a method of making a nonwoven web includes dispensinga fluid stream from a first source, wherein the fluid stream includesfiber. The method further includes collecting fiber on a receivingregion situated proximal and downstream to the source. The receivingregion is designed to receive the flow stream dispensed from the sourceand form a wet layer by collecting the fiber. A further step of themethod is drying the wet layer to form the nonwoven web.

In another embodiment, a method of making a nonwoven web includesproviding a furnish from a source, the furnish including at least afirst fiber, and dispensing a stream of the furnish from an apparatusfor making a nonwoven web. The method further includes collecting fiberpassing through the opening on a receiving region situated downstreamfrom the source, collecting a remainder of fiber on the receiving regionat a downstream portion of the mixing partition, and drying the wetlayer to form the nonwoven web.

In one wet laid processing embodiment, the medium is made from anaqueous furnish comprising a dispersion of fibrous material and othercomponents as needed in an aqueous medium. The aqueous liquid of thedispersion is generally water, but may include various other materialssuch as pH adjusting materials, surfactants, defoamers, flameretardants, viscosity modifiers, media treatments, colorants and thelike. The aqueous liquid is usually drained from the dispersion byconducting the dispersion onto a screen, inclined screen or otherperforated support retaining the dispersed solids and passing the liquidto yield a wet media composition. The wet composition, once formed onthe support, is usually further dewatered by vacuum or other pressureforces and further dried by evaporating the remaining liquid. Optionsfor removal of liquid include gravity drainage devices, one or morevacuum devices, one or more table rolls, vacuum foils, vacuum rolls, ora combination thereof. The apparatus can include a drying sectionproximal and downstream to the receiving region. Options for the dryingsection include a drying can section, one or more IR heaters, one ormore UV heaters, a through-air dryer, a transfer wire, a conveyor, or acombination thereof.

After liquid is removed, heating to induce thermal bonding can takeplace where appropriate by melting some portion of the thermoplasticfiber, resin or other portion of the formed web material. Otherpost-treatment procedures are also possible in various embodiments,including chemical treatment, resin curing steps. Pressing, heattreatment and additive treatment are examples of post-treatment that cantake place prior to collection from the wire. After collection from thewire further treatments such drying and calendaring of the fibrous matmay be conducted in finishing processes.

One specific machine that can be used as described herein is theDeltaformer™ machine (available from Glens Falls Interweb, Inc. of SouthGlens Falls, N.Y.), which is a machine designed to form very dilutefiber slurries into fibrous media. Such a machine is useful where, e.g.inorganic or organic fibers with relatively long fiber lengths for awet-laid process are used, because large volumes of water must be usedto disperse the fibers and to keep them from entangling with each otherin the furnish. Long fiber in wet laid process typically means fiberwith a length greater than 4 mm, that can range from 5 to 10 mm andgreater. Nylon fibers, bi-component fiber, cotton linter, polyesterfibers (such as Dacron®), regenerated cellulose (rayon) fibers, acrylicfibers (such as Orlon®), cotton fluff fibers, polyolefin fibers (i.e.polypropylene, polyethylene, copolymers thereof, and the like), andabaca (Manila Hemp) fibers are examples of fibers that areadvantageously formed into fibrous media using such a modified inclinedpapermaking machine.

The Deltaformer™ machine differs from a traditional Fourdrinier machinein that the wire section is set at an incline, forcing slurries to flowupward against gravity as they leave the headbox. The incline stabilizesthe flow pattern of the dilute solutions and helps control drainage ofdilute solutions. A vacuum forming box with multiple compartments aidsin the control of drainage. These modifications provide a means to formdilute slurries into fibrous media having improved uniformity ofproperties, across the web when compared to a traditional Fourdrinierdesign.

In one embodiment of the wet section, mixtures of fibers and fluid areprovided as a furnish after a separate furnish making process. Thefurnish can be mixed with additives before being passed onto the nextstep in the medium forming process. In another embodiment, dry fiberscan be used to make the furnish by sending dry fibers and fluid througha refiner which can be part of the wet section. In the refiner, fibersare subjected to high pressure pulses between bars on rotating refinerdiscs. This breaks up the dried fibers and further disperses them influid such as water that is provided to the refiner. Washing andde-aeration can also be performed at this stage.

After furnish making is complete, the furnish can enter the structurethat is the source of the flow stream, such as a head box. The sourcestructure disperses the furnish across a width loads it onto a movingwire mesh conveyor with a jet from an opening. In some embodimentsdescribed herein, two sources or two headboxes are included in theapparatus. Different headbox configurations are useful in providingmedia. In one configuration, top and bottom headboxes are stacked righton top of each other. In other configuration, top and bottom headboxesare staggered somewhat. The top headbox can be further down the machinedirection, while the bottom headbox is upstream.

In one embodiment, the jet is a fluid that urges, moves or propels afurnish, such as water or air. Streaming in the jet can create somefiber alignment, which can be partly controlled by adjusting the speeddifference between the jet and the wire mesh conveyor. The wire revolvesaround a forward drive roll, or breast roll, from under the headbox,past the headbox where the furnish is applied, and onto what is commonlycalled the forming board.

The forming board works with the furnish, which is leveled and alignmentof fibers can be adjusted in preparation for water removal. Further downthe process line, drainage boxes (also referred to as the drainagesection) remove liquid from the medium with or without vacuum. Near theend of the wire mesh conveyor, another roll often referred to as a couchroll removes residual liquid with a vacuum that is a higher vacuum forcethan previously present in the line.

The medium described herein can be assembled with other conventionalfilter structures to make a filter composite layer or filter unit. Themedium can be assembled with a base layer which can be a membrane, acellulosic medium, a synthetic medium, a scrim or an expanded metalsupport. The medium can be used in conjunction with many other types ofmedia, such as conventional media, to improve filter performance orlifetime.

A perforate structure can be used to support the media under theinfluence of fluid under pressure passing through the media. The filterstructure of the invention can also be combined with additional layersof a perforate structure, a scrim, such as a high-permeability,mechanically-stable scrim, and additional filtration layers such as aseparate loading layer. In one embodiment, such a multi-region mediacombination is housed in a filter cartridge commonly used in thefiltration of non-aqueous liquids.

The non-woven webs of the invention include fibers in a thermally bondedweb, wherein the web includes a bi-component fiber having a core polymerand a shell polymer, the shell having a melting point that is greaterthan about 115° C., wherein the bi-component fiber has a diameter ofabout 5 to 25 μm and a length of about 2 to 15 μm; and a cellulosic orsynthetic polymer fiber; wherein the web is substantially free of aglass fiber. The shell polymer melting point can be between 120° C. and180° C., and in preferred embodiments about 140° C. to 160° C. Incore/shell embodiments, the core polymer melting point temperature ishigher than the melting point of the shell. In some embodiments, thesecond, or core, polymer melting point is at least about 240° C. Thebi-component fiber diameter is about 5 to 50 micrometers often about 10to 20 micrometers and typically in a fiber form generally have a lengthof 0.1 to 20 millimeters or often have a length of about 0.2 to about 15millimeters.

In some embodiments of the non-woven webs of the invention describedabove, the thermally bonded web has about 1 to 30 wt. % of thebi-component fiber and 70 to 99 wt. % of the staple fiber, and the webhas a thickness of about 0.2 to 2 mm, a solidity of about 1 to 20% orabout 2 to 10%, a basis weight of about 45 to 150 g-m⁻², a pore size ofabout 12 to 50 microns, and a permeability of about 1.5 to 3 msec. Insome embodiments, the thermally bonded web has about 0.1 to 50 wt % ofthe bi-component fiber and about 50 to 99.9 wt % of the staple fiber. Insome embodiments the web has a thickness of about 0.1 mm to 2 cm. Insome embodiments the web has a solidity of about 1 to 20%. In someembodiments the web has a basis weight of about 20 to 300 g-m⁻² or about50 to 130 g-m⁻². In some embodiments, the web has a pore size of about 5to 150 microns. In some embodiments, the web has a permeability of about0.5 to 10 m/sec. In some embodiments, the staple fiber is either about 1to 20 wt-% of a cellulosic fiber or about 10 to about 50 wt % of apolyester fiber.

In some embodiments of the nonwoven webs described above, the staplefiber is a blend of both cellulosic fiber and polyester fiber, whereinthe blend is composed of about 1 to 20 wt-% of a cellulosic fiber andabout 10 to about 50 wt % of a polyester fiber relative to the weight ofthe web. In some embodiments, the staple fiber is either about 5 to 15wt-% of a cotton linter fiber or about 10 to about 50 wt % of apolyester fiber. In some embodiments the staple fiber is a blend of bothcotton linter fiber and polyester fiber, wherein the blend is composedof about 5 to 15 wt-% of a cotton linter fiber and about 10 to about 50wt % of a polyester fiber relative to the weight of the web. In someembodiments, the web has about 1 to 30 wt. % of the bi-component fiberand 70 to 99 wt. % of the staple fiber, and the web has a thickness ofabout 0.2 to 2 mm, a solidity of about 1 to 20% or about 2 to 10%, abasis weight of about 45 to 150 g-m⁻², a pore size of about 12 to 50microns, and a permeability of about 1.5 to 3 msec. In some embodiments,the thermally bonded web has about 0.1 to 50 wt % of the bi-componentfiber and about 50 to 99.9 wt % of the staple fiber. In some embodimentsthe web has a thickness of about 0.1 mm to 2 cm. In some embodiments theweb has a solidity of about 1 to 20%. In some embodiments the web has abasis weight of about 20 to 300 g-m⁻² or about 50 to 130 g-m⁻². In someembodiments, the web has a pore size of about 5 to 150 microns. In someembodiments, the web has a permeability of about 0.5 to 10 msec. In someembodiments, the staple fiber is either about 1 to 20 wt-% of acellulosic fiber or about 10 to about 50 wt % of a polyester fiber.

In embodiments, the non-woven webs of the invention include fibers in athermally bonded web, wherein the web includes

-   -   (a) about 1 to 30 wt. % based on the weight of the web of a        first bi-component fiber having a first core polymer and a first        shell polymer, wherein the first shell polymer has a melting        point of up to 115° C., and the first bi-component fiber has a        diameter of about 5 to 25 μm and a length of about 2 to 15 mm;    -   (b) about 5 to 50 wt. % based on the weight of the web of a        second bi-component fiber having a second core polymer and a        second shell polymer, wherein the second shell polymer has a        melting point of about 120° C. to 170° C.; and the second        bi-component fiber has a fiber diameter of about 5 to 25 microns        and a fiber length of about 2 to 15 mm; and    -   (c) about 10 to 80 wt. % based on the weight of the web of a        staple fiber; wherein the web has the thickness of about 0.25 to        2 mm, a solidity of about 5-10%, a basis weight of about 45 to        150 g-m⁻², a pore size of about 12 to about 50 microns, and a        permeability of about 1.5 to 3 msec. In some such embodiments,        the melting point of the second shell polymer is about 140° C.        to 160° C. In some such embodiments, the first bi-component        fiber and the second bi-component fiber are core/shell fibers        having first and second core polymers having a melting point of        240 to 260° C. In some such embodiments, the web has a basis        weight of about 50 to about 130 g-m⁻². In some such embodiments,        the web is substantially glass free. In some such embodiments        the staple fiber includes about 1 to 20 wt-% of a cellulosic        fiber and about 10 to 50 wt % of a polyester fiber. In some such        embodiments the staple fiber includes about 5 to 15 wt-% of a        cotton linter fiber and about 10 to 50 wt % of a polyester        fiber.

In embodiments, the non-woven webs of the invention include fibers in athermally bonded web that is substantially free of a glass fiber,wherein the web includes

-   -   (a) about 1 to 15 wt. % of a first bi-component fiber having a        first core polymer with a melting point of 240° to 260° C. and a        first shell polymer with a melting point of 100° to 115° C.;        wherein the first bi-component fiber has a diameter of about 10        to 15 μm and a fiber length of about 0.3 to 0.9 cm;    -   (b) about 5 to 50 wt. % of a second bi-component fiber having a        second core polymer with a melting point of 240° to 260° C. and        a second shell polymer with a melting point of 120° to 160° C.;        wherein the second bi-component fiber has a diameter of about 10        to 15 microns and a fiber length of about 0.3 to 0.9        centimeters;    -   (c) about 1 to 20 wt. % of a cotton linter fiber; and    -   (d) about 10 to 50 wt. % of a polyester fiber.        In some such embodiments, the melting point of the second shell        polymers is about 140°-160° C. In some such embodiments the        polyester fiber comprises about 1 to 20 wt. % of a staple fiber        having a diameter of 7 to 15 μm and a cellulosic or cotton fiber        having a diameter of 15 to 55 μm, and the ratio of the diameters        of the first polyester fiber to the second polyester fiber is        about 1:1.2 to 5.

Embodiments of the invention include method of making a nonwoven webincluding a thermally bonded web, the method involving:

-   -   (a) forming a furnish including an aqueous concentration of        solids of about 0.005 to 5 or 0.005 to 7 wt. % the solids        including about 20 to about 60 wt. % of a bi-component fiber,        about 5 to about 25 wt. % of a cotton linter fiber, and about 10        to 50 wt. % of a staple polyester fiber having a diameter of        about 7 to about 15 μm and a fiber length of about 3 to about 10        mm;    -   (b) contacting the furnish with an inclined screen to form a wet        layer; and    -   (c) drying wet layer to form a web.        In some such embodiments, the polyester fiber includes about 1        to 20 wt. % of a staple fiber having a diameter of 7 to 15 μm        and a cellulosic or cotton fiber having a diameter of 15 to 55        μm, and the ratio of the diameters of the first polyester fiber        to the second polyester fiber is about 1:1.2 to 1:5.

Furnishes were formulated to produce nonwoven webs having improvedproperties property. Examples 1-3 shows compositional information aboutthe furnish formulations. The following different fibers were used inthe furnish examples listed in Table 1, where an abbreviation for eachfiber is provided in parenthesis:

-   -   1. A polyester bi-component fiber known as 271P available        from E. I. DuPont Nemours, Wilmington Del. with a sheath melt        temperature of about 73° C. The average fiber diameter of 271P        is about 13 microns and length is 6 mm.    -   2. Bi-component fiber known as a short-cut fiber made of a        polyester/co-polyester mix, consisting of 49.5% polyethylene        terephthalate, 47% co-polyester and 2.5% polyethylene copolymer        (BI-CO). One example of such a fiber is TJ04BN SD 2.2X5        available from Teijin Fibers Limited of Osaka, Japan with a        sheath melt temperature of about 155° C. The average fiber        diameter is 13 microns and length is 6 mm.    -   3. Cellulosic cotton linter fiber Buckeye Corp source fiber.    -   4. Polyester Fiber (P20FM) or Invista 205 WSD available from        Barnet USA of Arcadia, S.C.        In these examples, sulfuric acid was added to adjust the pH to        approximately 3.0 to disperse the fibers in the aqueous        suspension. The fiber content was approximately 0.03% (wt. %) in        the aqueous suspensions of the furnishes used to make the media        in the examples. The furnishes containing dispersed fibers were        stored in their respective machine chests (storage tanks) for        subsequent use. During media manufacturing, the furnish streams        were fed to their respective headboxes after appropriate        dilution.

TABLE 3 Exemplary Materials Function Fiber Identity % Example 1Bi-component TJ04BN 39.2 Binder Fiber Bi-component 271P 9.8 Binder FiberStaple Fiber Cotton linter 7.35 1 - Buckeye 29 μm Cellulose 512 StapleFiber 7.2 μm PET 41.65 2 - Invista 205 WSD PET Hydrophobic C₆Fluorochemical 2 Additive - Phobol Poly-fluoro-acrylic Additive Example2 Binder Fiber TJ04BN 40 Binder Fiber 271P 10 Staple Fiber 512 CottonLinters 7.5 1 - Buckeye 512 Staple Fiber 205WSD 42.5 2 - Invista PETExample 3 Binder Fiber TJ04BN 40 Binder Fiber 271P 10 Staple Fiber 512Cotton Linters 10 1 - Buckeye 512 Staple Fiber 205WSD 17.5 2 - InvistaPET Staple Fiber P30FM staple PET 22.5 3 - Barnet

TABLE 4 Comparative Materials Function Fiber Identity % ComparativeExample 1 Bi-component 271P 50 Binder Fiber Staple PET 205WSD 40 Glassfiber Owens 11 μm glass 10 Corning Comparative Example 2 Bi-componentTJ04BN 40 Binder Fiber Binder Fiber 271P 10 Staple glass 11 μm glass 10Staple PET 205WSD 7

Other variables on the machine that are adjusted during the formation ofthe media include pulper consistency, incline angle of the initialmixing partition, incline angle of the machine, incline angle of theextended mixing partition, basis weight, machine speed, heel height,furnish flow, head box flow, head box consistency, and drainage boxcollection. Resultant media may be post-treated, typically with a singleweb treatment process step, for example, with chemical treatment,additives, calendaring, heat or other methods and equipment familiar inthe art to provide a finished gradient fibrous mat.

Tensile breaking strength of test sample strips, and breaking load andstretch are measured following the procedure in TAPPI T 404. Additionalrequirements for testing of pulp hand sheets are detailed in standardTAPPI 220. These include evaluation of bursting strength, tensilebreaking load; breaking length and tear factor. Tensile EnergyAbsorption—Tensile energy absorption (TEA) of paper is defined as thearea under the load-elongation curve (i.e., energy) related to thesurface area of paper between the grips. This result is typically usedto characterize the energy absorbing capacity of paper (see TAPPI T494), and use of a microprocessor or computer to calculate energygreatly simplifies data reduction. Measuring Stretch—The amount ofstretch in paper and board is a critical measure of quality, since it isa necessary requirement for a sheet to fold well and resist local stresswhen used in packaging, corrugated board and tissues. We suggest thatafter initially clamping a sample in the upper grip, to apply a smallstress to remove waviness. The sample is then pulled to rupture within aspecified time, as detailed in T 457. When TEA measurement is required,a constant rate of elongation tester with a plotter in accordance withTAAPPI specification T494-os is used. A sample is made using a 1×6″ diecutter. The sample is cured, if needed, in an oven capable ofmaintaining 149° C. In the test two representative samples havingdimensions of 178×178 mm are taken. Care is taken to make sure that thesamples have been cured at or above the melting point of the microphonefiber. From the samples, three specimens in each of the machine andcross machine direction having dimensions of 25.4×152 mm are obtained.The specimens are dried for 24 hours. If the specimens are to be testedin a white condition the specimens are immersed into distilled watercontaining 1% Triton-100 surfactant. Once saturated the samples areremoved blotted to remove excess liquid and tested. The samples areclamped into the tester in the upper and lower jaw set at 4 inchesapart. The tester is set to stress the sample at 2 in./min. The testeris operated and any specimen failure is noted. If no failure as noted,the tensile breaking strength and pounds or kilograms force is recorded.Using the data the average tensile breaking strength or TE a resultingfrom three successful tests is reported along with the wet or dry natureof the sample the machine direction and any other relevant notation.

TABLE 5 Tensile data TEA Tensile Testing Media Comparison ParameterComp. Ex. 1 Ex. 4 Burst kPa 175 208 Burst psi 25.4 30.2 Hot TensileTesting Comparative Example Test Temp Parameter Ex. 1 4  22° C. lbs/inch4.52 8.02  80° C. lbs/inch 2.9 4.3 100° C. lbs/inch 1.42 2.6 110° C.lbs/inch 0.79 2.1 120° C. lbs/inch 0.07 2 130° C. lbs/inch 0 1.2 135° C.lbs/inch 0 1 140° C. lbs/inch 0 0.67In these tables, the burst strength and hot tensile strength of theclaimed materials is better than the comparative examples and theimproved strength as temperature is increased is also seen.

While the invention has been described in connection with specificembodiments thereof, it will be understood that it is capable of furthermodifications and this application is intended to cover any variations,uses, or adaptations of the invention following, in general, theprinciples of the invention and including such departures from thepresent disclosure as come with known or customary practice within theart to which the invention pertains and as may be applied to theessential features hereinbefore set forth and as follows in scope of theappended claims.

We claim:
 1. A filter element comprising a filter medium comprising amedia layer comprising fibers in a thermally bonded nonwoven web, theweb comprising: (a) a bi-component fiber having a structural polymerportion and a thermoplastic binder polymer portion, wherein thestructural polymer portion has a melting point of at least 240 ° C. andthe binder polymer portion has a melting point of up to 115 ° C.; andthe bi-component fiber has a diameter of about 5 μm to 25 μm; (b) abi-component fiber having a structural polymer portion and athermoplastic binder polymer portion, wherein the structural polymerportion has a melting point of at least 240 ° C. and the binder polymerportion has a melting point of 120 ° C. to 170 ° C.; and thebi-component fiber has a diameter of about 5 μm to 25 μm; and (c) astaple fiber; wherein the web comprises about 5 wt-% to 25 wt-%, basedon the weight of the web, of the bi-component fiber of part (a); whereinthe web comprises about 25 wt-% to 60 wt-%, based on the weight of theweb, of the bi-component fiber of part (b); and wherein the web has asolidity of under 10 %.
 2. The filter element of claim 1, the webcomprising about 10 wt-% to 70 wt-%, based on the weight of the web, ofthe staple fiber; and wherein the web has a thickness of about 0.1 mm to2 cm.
 3. The filter element of claim 1, wherein the bi-component fibersof (a) and (b) have a length of about 2 mm to about 15 mm.
 4. The filterelement of claim 1, wherein the web has a basis weight of about 45 g/m²to 150 g/m^(2.)
 5. The filter element of claim 1, wherein the web has abasis weight of about 20 g/m² to about 300 g/m^(2.)
 6. The filterelement of claim 1, wherein the web has a pore size of about 12 μm to 50μm.
 7. The filter element of claim 1, wherein the web has a permeabilityof about 1.5 m/s to 3 m/s.
 8. The filter element of claim 1, wherein thestaple fiber comprises a combination of about 1 wt-% to about 20 wt-% ofa cellulosic fiber, and about 10 wt-% to about 50 wt-% of a polyesterfiber.
 9. The filter element of claim 1, wherein the staple fibercomprises a combination of about 5 wt-% to 15 wt-% of a cotton linterfiber, and about 10 wt-% to about 50 wt-% of a polyester fiber.
 10. Thefilter element of claim 1, wherein the staple fiber comprises cottonlinter fiber having a length of 0.5 mm to 4 mm and diameter of 15 μm to55 μm.
 11. A filter element comprising a filter medium comprising amedia layer comprising fibers in a thermally bonded nonwoven web, theweb comprising: (a) about 5 wt-% to 25 wt-%, based on the weight of theweb, of a bi-component fiber having a core polymer and a shell polymer,wherein the core polymer has a melting point of at least 240 ° C. andthe shell polymer has a melting point of up to 115 ° C.; and thebi-component fiber has a diameter of about 5 μm to about 25 μm and alength of about 2 mm to about 15 mm; (b) about 25 wt-% to 60 wt-%, basedon the weight of the web, of a bi-component fiber having a core polymerand a shell polymer, wherein the core polymer has a melting point of atleast 240° C. and the shell polymer has a melting point of 120 ° to 170° C.; and the bi-component fiber has a diameter of about 5 μm to about25 μm and a length of about 2 mm to about 15 mm; and (c) about 10 wt-%to 70 wt-%, based on the weight of the web, of a staple fiber; whereinthe web has a thickness of about 0.25 mm to about 2 mm, a solidity ofunder 10 %, a basis weight of about 45 g/m² to about 150 g/m² , a poresize of about 12 μm to about 50 μm, and a permeability of about 1.5 m/sto about 3 m/s.
 12. The filter element of claim 11, wherein the meltingpoint of the shell polymer of part (b) is about 140 ° C. to about 160 °C.
 13. The filter element of claim 11, wherein the core polymers of part(a) and part (b) have a melting point of 240° C. to about 260 ° C. 14.The filter element of claim 11, wherein the web has a basis weight ofabout 50 g/m² to 130 g/m^(2 .)
 15. The filter element of claim 11,wherein the web is substantially glass free.
 16. The filter element ofclaim 11, wherein the staple fiber comprises about 15 wt-% to 50 wt-% ofthe web and comprise a cellulosic fiber or a polyester fiber, or amixture thereof.
 17. The filter element of claim 11, wherein the staplefiber comprises a combination of about 5 wt-% to 15 wt-% of a cottonlinter fiber, and about 10 wt-% to 50 wt-% of a polyester fiber.
 18. Thefilter element of claim 11, wherein the web has a wet bursting strengthof greater than about 5 lb/in^(2.)
 19. A filter element comprising afilter medium comprising a media layer comprising fibers in a thermallybonded nonwoven web, the web comprising: (a) a bi-component fiber havinga structural polymer portion and a thermoplastic binder polymer portion,wherein the structural polymer portion has a melting point of at least240 ° C. and the binder polymer portion has a melting point of up to 115° C.; and the bi-component fiber has a diameter of about 5 μm to 25 μm;(b) a bi-component fiber having a structural polymer portion and athermoplastic binder polymer portion, wherein the structural polymerportion has a melting point of at least 240 ° C. and the binder polymerportion has a melting point of 120 ° C. to 170 ° C.; and thebi-component fiber has a diameter of about 5 μm to 25 μm; and (c) astaple fiber; wherein the web has a solidity of under 10% and a wetbursting strength of greater than about 5 lb/in^(2;) wherein the webcomprises about 5 wt-% to 25 wt-%, based on the weight of the web, ofthe bi-component fiber of part (a); and wherein the web comprises about25 wt-% to 60 wt-%, based on the weight of the web, of the bi-componentfiber of part (b).
 20. The filter element of claim 19, wherein the wetbursting strength of the web is 10 lb/in² to 20 lb/in^(2.)
 21. A filterelement comprising a filter medium comprising a media layer comprisingfibers in a thermally bonded nonwoven web, the web comprising: (a) abi-component fiber having a structural polymer portion and athermoplastic binder polymer portion, wherein the structural polymerportion has a melting point of at least 240 ° C. and the binder polymerportion has a melting point of about 73 ° C.; and the bi-component fiberhas a diameter of about 5 μm to 25 μm and a length of 0.3 cm to 0.9 cm;(b) a bi-component fiber having a structural polymer portion and athermoplastic binder polymer portion, wherein the structural polymerportion has a melting point of at least 240 ° C. and the binder polymerportion has a melting point of about 155 ° C.; and the bi-componentfiber has a diameter of about 5 μm to 25 μm and a length of 0.3 xm to0.9 cm; and (c) a staple fiber; wherein the web comprises about 5 wt-%to 25 wt-%, based on the weight of the web, of the bi-component fiber ofpart (a); wherein the web comprises about 25 wt-% to 60 wt-%, based onthe weight of the web, of the bi-component fiber of part (b); andwherein the web has a solidity of under 10 %.
 22. The filter element ofclaim 21, wherein the web has a wet bursting strength of greater thanabout 5 lb/in^(2.)
 23. The filter element of claim 21, wherein the webhas a tensile strength of greater than about 2 lb/in at 100 ° C.